Goodneighbor- like, five quests and... that's it.
The Memory Den- falls under Goodneighbor, but once you do the little Kellogg set piece, there is literally no interaction with it... I can't even talk to Doctor Amari or that Cabaret lady. It's just sort of there.
The Gunners- yet another Talon Company-esque corporate mercenaries- a massive amount of tech, hardware and power... no interactions outside of "kill" and "pay toll". No deeper story as far as I've found. Dspite being one of the best outfitted groups in the Commonwealth, they haven't tried to actually build a nation... hell, who's paying them to do all this shit? What's the point in it? Surely they should be coercing farmsteads into joining them, assaluting larger towns? But nope, they're just harassing the Minutemen and setting up camps.
Vault 75- like all of the votes, the sense of discovery felt limited. There was no real "payoff" hen the end of the experiment was made manifest. It also could've served as an explanation for the origin of the Gunners.
The Minutemen- incredibly generic good guys, with no real history.
Diamond City Science Center- this one really bugged me, but it's a little thing. I just wished it had more ways to interact with it- I really enjoy learning about Wasteland biology, but we basically just got the opportunity for Bloatflies.
Diamond City- I don't even care about the size- so few quests, so little interactivity. Like, the upper seats are relevant in I think literally one quest.
The Institute- could've had actual moral justifications for what they did. But nope- they admitted they were sentient, but just kept using them. Hell, I wrote up a better scenario for the Institute in the weeks prior to the game. Speaking of which...
Androids- Sure, it's done to death, it would've been too Blade Runner, but I really feel like hammering home themes of sapience, what makes us human, how can we tell another being is sentient, etc would've been better than themes about... uh... family... and war never changes... and... uh...