Settlement building, I couldn't tell you why it's there other than "it's just there to say it's there". You build a little town out of big piles of junk.
You have a bunch of nameless NPCs called "settler" with as much personality as cardboard cutouts, this was supposed to be the replacement for interesting NPCs. I think it's just an excuse to avoid creating interesting NPCs which they are obviously too incompetent to create.
I think I could have made this work, well at least building your own settlement.
First of all, I would kick out the whole minecraft stuff. You don't actually build the buildings, furniture or machines yourself. At best you can plan where buildings are placed.
There would only be one settlement, and you would have to do some quests before you are elected mayor and can run it.
You would have to start recruiting people like carpenters, electricians, skilled people like then, thus lots of speech/charisma checks.
Alternatively you can buy or free slaves with those skills and send them to your new settlement.
You would also have to convince people with supportive skills such as defenders, teachers and doctors to go there as otherwise your settlement might not last long.
You would have to make arrangements with traders and caravan houses to start sending materials there. Depending on who you deal with and how much money is involved buildings would either be made of scrap or wood, or would be adobe buildings or buildings made from bricks. (the more you invest, the better)
The better your settlement does the more people would come to it. Likewise depending on how rich your settlement is elements such as facilities and defenses would improve.
Big strong walls and automated turrets around your settlement, a power plant and water purification. (these installations would be there but need to be fixed up by skilled people), workshops where advanced equipment and tools are made, and so on.
Perhaps some high tier equipment and weapons would only be available through making a successful settlement.
And your settlement would have an impact on the end game, either becoming a member of an emerging nation of perhaps the very capital.