I like settlements too - it is an original idea. And to be honest: This would not have been possible in Fallout 1/2 because there is no way the engine would support it. So why not now, when it can be done?
But I think there need to be some finishing touches on settlements, because there are some rough edges.
Building could be a bit more flexible, it should not be necessary to use tricks to place items.
Pathing and NPC activities are also a bit rough: I built a normal wooden home on a leveling platform (the floor element on wooden stakes). The entrance of the house needed a ladder. All build with no tricks, all snapped together fine. But NPCs have serious trouble to negotiate the ladder, the seem always to hang in the middle, because they want to walk sideways on the ladder.
Defending a settlement: It makes only sense when you are there, then placement of turrets, walls and guards matter. If you are not there, the cell is not loaded, and no fight can take place. This was always so with this engine - I watched it in FO3 with the trading caravans.
So the designers had to build a penalty if you ignore the call to help defend a settlement - and this needs a touch too: There are reports of people who had insanely big defense values and still lost when they were not there. Obviously, if the cell is never loaded no fight will take place, the placement of defenses does not matter at all. So it is a 'scripted resolution' if you never show up. This could use some touches too. For example a 'Attackers have been driven off' when your defenses are 2 or 3 times better than the minimum.
But the interesting things where you see how good your defenses are will only happen if you go there. I had normal defenses in the Starlight Drive In (2 points over minimum), and around 8 gunners attacked in 2 or 3 waves. They were all killed by settlers and the turrets, I did nearly nothing.
So - yes I like it. Is it Fallout? It is in a new way, it should not be the main task in the game or it will be Fallsim, but as a nice additional touch and an original idea it is fine.