First off, this being a game set in a different universe with different natural laws, it doesn't actually NEED to conform to reality.
Second, just how many Deathclaws, Super Mutants, Raider Gangs, Feral Ghouls, Rad Scorpions, Radiation Storms etc. did the Industrial Revolution have to contend with and do it where the closest thing to a central authority was the village elders?
A better comparison would be how long did it take for Western Civilization to recover after the fall of the Roman Empire? This is a better comparison, but not a good one. Primarily because the "Fall of the Roman Empire" is kind of a vague term. It can be dated in the 5th Century or the 15th Century depending on how you want to define "Roman Empire".
Oddly, this period between the collapse of the Western Roman Empire (5th Century) and the collapse of the Eastern Roman Empire (Constantinople in the 15th Century) is quite often referred to as the Dark Age in Western Europe. That is 1000 years of regression, not progress, in Western Europe where the people were picking over the bones of Rome. (In and around Rome itself, people had a habit of knocking down Empire structures to use as building materials for their more primitive structures.) This regression occurred in spite of Roman Technology still being in use and being expanded upon in the Byzantine Empire practically RIGHT NEXT DOOR.
There is a substance known as Roman Concrete. Romans used it in just about everything they built was made of it. The knowledge of how to make it was even written down and was salted away as far back as 50 BC. In the 5th Century it stopped being used for construction in Western Europe and wasn't reinvented until the 18th Century (btw, that is 300 years AFTER the Dark Ages ended). What we use today is quite often referred to as Portland Cement. It isn't the same thing as Roman Concrete and in many ways is inferior to Roman Concrete. It took about 150 years to develop. And those dusty scrolls that were written in 50 BC still exist.
There is no doubt that many Romans survived the "Fall of Rome". There is no doubt that many Roman engineers survived the "Fall of Rome". So what do you think that our heroic Roman engineer had as a priority on teaching his kids after the "Fall of Rome"? Was it how to feed themselves and defend against the various bandits roaming the land? Or did he teach them how to mix concrete and use it to build a freaking dome for the Pantheon (which by the way would involve him teaching his kids how to do math with that brain damaged number system)? The people of Western Europe at that time were pretty much stuck in that old adage, "When you are up to your ass in alligators, it is hard to remember that the original idea was to drain the swamp."
The "Fall of America" did not happen over time. It happened over the space of a couple of hours. There is no Constantinople just over the hill that can serve as a shining example of what can be because the "Fall of America" was in reality the "Fall of Everywhere". There is nothing left but the dismembered corpse of What Was. The land and everything that walks on it, tunnels under it or flies over it has been poisoned, twisted and then turned against our species. The people of the wasteland are in the same swamp as the people of the Dark Ages, except that the swamp is irradiated and the alligators in the swamp would be a blessing compared to what ate them.
I have no idea why some people keep insisting that the wasteland would be something other than the absolute hell hole it is (besides, do you people really, really, really want a Fallout game based around a 9 to 5 job in a cubicle farm?) btw, this is not something I am accusing the OP of.
As for a total lack of industry. Just because we don't see it doesn't mean it isn't there and we actually do see some of it. As an example: There is a person out there that is canning meat (a minor spoiler: do NOT eat it. It won't kill you but still, don't eat it) and at least one trader is distributing it.
Fallout robots are both quite intelligent and slavishly stupid. Curie is a perfect example. She was set a task to accomplish and told to wait for someone from Vault-Tek to arrive and take possession of the final product. She completed the experiments and then sat there in a locked room. She want to leave and go exploring and she has the capability to open the door (in fact, she is the only one that can open it), but that was not within her instructions. So instead she sat locked in that room with her proverbial thumb stuffed up her thruster as far as it would go for over 80 years. So basically, robots will typically not do anything outside of their instruction set.
This brings up Ironsides and the USS Constitution. Evidence suggests that he recruited (technically speaking, he Impressed them, aka. Shanghaied) his crew by reprogramming them, but that doesn't explain him. The simple answer is that we don't know how he got started on his quest to get the USS Constitution to the Atlantic so he can fight the Chinese, but that is his current instruction set and he will not deviate from it until his instruction set is changed. So the answer as to why functioning robots wouldn't repair and maintain a factory is quite simple, they either weren't instructed to to begin with or they have run out of maintenance supplies. The robots in the cannery are certainly keeping things running for the human that is control of it.
Yes, for us to be able to build settlements, there has to be an ability to take raw materials and turn them into the intermediate materials we use for construction. For game play there is no real purpose of showing how a wall is made or showing the tools required unless we are going to be forced to do those stages. Quite a few people enjoy the building experience as it is now. How many of them would if they were required to use a forge to make metal sheets and a sawmill to make boards or even be required to take all this scrap to someones foundry or sawmill and have it done for them?
There are holes like this in all the Fallout games, there pretty much has to be. Bethesda Game Studios and all other game studios cannot fully flesh out a world space of this size, and even if they could, it probably would not fit on anyone's hard drive. They have to leave gaps that the player's imagination must fill. Now, now you can argue they left out something when they shouldn't have, but you can't really fault them for leaving some things out.