This is a sentiment that has been echoed before, but I wanted to bring it up again because I wanted to highlight how I feel future content updates, mods, or dlc could hopefully improve upon this aspect of the game.
To begin, I had high hopes for the settlement system. When FO4 was introduced at E3, I dared to hope that this might be my "dream" game; in the sense that it would blend together an exciting world filled with intriguing characters, locations, and events with a more monotonous, slow paced, simulatory experience... a la The Sims or Harvest Moon. I got excited thinking about playing Fallout 4 as a hardened adventurer, who went back to his settlements to rest, resupply, and find companionship.
The reality of the situation is that the settlement building only really serves as an RP device, which isn't horrible! I have gotten a lot of enjoyment out of building settlements and RPing that I have a home and spend time with my romantic interests and what not. Problem is, it is a far cry from what I imagined it would be like and it is incredibly buggy. It will be best to break down my complaints into smaller points and then summarize how I think to improve it.
The Bad
1. Incredibly Buggy
The interface for keeping track of settlements is consistently off. Happiness appears to be all over the place and at one point I apparently had 1 settler at The Castle, when in reality it had 11 people. One of my settlements is littered with ghoul bodies that will not go away, and that problem can similarly persist in other places (most notably the body right outside of Sanctuary). For a purely ancillary game device, little hiccups that steal the small joy and immersion to be had are almost crushing. These need to be addressed first and foremost.
2. Completely unimportant
This is a consequence of Bethesda's drive to have NOTHING slow the player down, which is admirable and good in some respects. For instance, do I really miss having to scrounge hunting rifles over and over to repair my favorite one? No. And yet, I also miss having to juggle SOMETHING. I feel like that is where settlements could have really shone, especially since expansion of the settlements required active participation on the part of the player. You get Sanctuary and Red Rocket out of the gate and then can leave it aside and have nothing really negative come back on you.
Spoiler
This is a problem, as one of the major themes of the entire game is the future of the Commonwealth, and the events of the story all move to make you an integral part of that future. And not just integral but active! I DO NOT think a player should be punished for NOT doing settlement quests, but that aspect of the game should be something they WANT to participate in, because it enriches the experience they could otherwise be having and extends the life of the game.
3. Settlements and their population are too static
Diamond City is pretty great the first time you see it, because DC has some interesting characters. I know you cannot have randomly generated people with the same breadth of personality, but giving them all names would be a great first start. Giving them unique radiant requests would be another. That would also be helpful when trying to assign jobs to settlers. I mean, Fallout Shelter had named vault dwellers for crying out loud. I'm starting to venture into how I think it should change, so I will stop where I'm at now and move onto it...
My fixes
1. Fix the bugs. Not much else to say on that point, although I'm sure it is easier said than done, but I have this reasonable expectation that once the mod kit hits officially, bugs will be non-existent thanks to the player base. That doesn't really speak highly of your studio if your consumers are better at your job than you are. And that might be unfair, but I'd like to think that the least your post-game support could include would be aggressive bug fixes. It just gives players a bad perception when it seems like mods do more in terms of quality control than your staff. As if you are too busy counting the greenbacks to care about delivering a game that fulfills (and hopefully exceeds) your expectations. Just food for thought.
2. Integrating the settlements more cohesively can be done in small steps, but will most likely require a major DLC to see it come to full fruition. I think the first and most sensible step would be the ability to lose settlements. Obviously, this needs to be done in the wake of an overhaul to the frequency of settlement attacks or what-have-you, but the ability to lose settlements to Super Mutants or Raiders (or synths, BoS, etc.) should be a very real threat. Losing a settlement in an attack would mean you arrive to a scene of carnage and must kill the enemy force before you can start to rebuild. A "morale meter" or some device would be extremely beneficial, because as you have the ability to lose settlements, you also have the ability to be deposed as the leader of the Minutemen. Lose too many settlements or mismanage defense too badly and you will be asked to step down. You can then choose to remain as a supporter or work your way back up through special radiant quests to resume control.
You care to keep your job and do it well, because you are looked upon as a hero, and your position should give you the ability to act like an actual general. I would sincerely appreciate new NPC dialogue that recognizes you upon entering your homesteads. The general population of your settlements should view you as the hero-general that you are and greet you as such. That dialogue should change over time as well and should ultimately reflect some of the decisions you make. Decisions like who to promote in your organization. I believe you should have the ability to promote different settlers in the Minutemen, so that some of them are designated soldiers and some are purely settlers/farmers/etc. You can then organize your militia and give them simple tasks, such as looking for supplies and ammo, patrolling a certain part of the Commonwealth, or protecting caravans. Your choices will be informed by which areas are being attacked and by the immediate needs of your people. You will also benefit from increases in morale for making smart decisions and some share of the spoils being found.
The key to all this, is that the changes I'm proposing do not tip the scales in the favor of the settlement system, but give incentives for a player to be an active participant in it. The more you invest, the more it feels like the organization is responding to your work. It would also make the Minutemen feel more like they are part of the world, rather than a static piece of it. For instance, you might encounter some of your patrols out in the Commonwealth when on a mission, and you get a radiant quest to assist them if they are in danger, or you can simply say hello and check to see how things are going. Imagine having the option to join them and help them complete their mission? That is a little bit of a stretch goal, but the point is to figure out how to make it feel like being part of the Minutemen is actually changing the game world positively. Settlements and the Minutemen are intricately intertwined and so being able to improve how you manage your role as the leader of the Minutemen will make settlement management overwhelmingly better as well.
This doesn't exhaust all the options to make settlements more integrated into the rest of the game, but it is a good start and I'm sure future mods/content updates will also see more improvements. I feel a DLC focused on what comes next after the conclusion of the main story would be a vital part of doing what I'm talking about here, as tacking it on wouldn't really enrich the experience at all. A DLC with the theme of restoring the Commonwealth that added more settlement features and functionality along with some new problem or force would inject the game with much more content that could be enjoyed long term, which is something I think that Bethesda games are all about. They are more in the Minecraft territory than they are in the Bioshock territory... if that makes any sense.
3. Giving settler's names is the first step. I think it would be fantastic if they could give the settlers certain affinities. For instance, when it comes time to assign a settler a job, maybe they have a few short lines about what they did before they arrived. If they mention being good at hunting, maybe you promote them into the militia, or perhaps they are simply survivors, in which case there isn't a right or wrong choice. Even better would be to have the settlers have opinions about what they would like to do! Imagine having a settlement filled with people who just wanted to farm and live and having to make the tough choice of choosing someone to serve in the militia. (As an aside, I understand the concept of a militia is citizen-soldiers, however I feel like if a future DLC is the way they go about this, the Minutemen might become a pseudo-military organization. So, maybe using the term militia is wrong, but I feel like having your populace separated into fighters and homesteaders is probably the way things would go naturally and it adds an interesting gameplay element).
I don't expect with the dialogue system that we have that there will be an abundance of talking points with the settlers, but having a few basic options that can be varied but used in Bethesda's radiant system would go a long way toward providing the illusion of a living populace, rather than just "video game people". Anything that helps make settlements feel on par with a town that has named NPCs living it in. Something a little bit more dynamic.
So those are my suggestions. I meant to keep that as concise as possible, so hopefully it was thorough enough to convey my ideas but not to drawn out so as to make people lose interest. I know a lot of threads on these forums are about sound bites, but I appreciate anyone who dives in and engages with my thoughts. Maybe if we can hash out our ideas, the developers will look at threads like this for inspiration. Either way, it beats complaining endlessly! I appreciate all feedback.