Been a while since i posted here but this caught my eye. In my personal opinion it comes down to replayability. Sure there are four factions to side with but the outcome for three of them is pretty much the same - Institute destroyed and then, depending on who you side with, either BOS or Railroad destroyed or neither, not a whole lot of variety tbh.
Furthermore unlike in NV, it doesn't really seem to impact the life in the commonwealth all that much, it always seemed to me, like the available factions mostly have impact on each other and not on the world at large. As for side quests, most have a binary or even in some cases, one outcome. The stories in side quests are nowhere near as captivating as in NV or hell, imo even in Fo3.
Yeah you mentioned mods but, the average player usually just plays the game vanilla, especially if they are on a console, even though they have mods now, console players just aren't very used to that. Don't get me wrong i enjoyed the hell out of that game but the fact that you have a pre-set backstory, that your character, presumably mostly remembers just takes out a lot of RP potential.
Yeah there are dick/slightly bad dialogue options and decisions but your character is kind of mostly always good/you can make an argument for every faction in the game that they are fighting for the greater good...That is, until the nuka world dlc, where if you want the access to all of the content, your character suddenly has to become an evil psychopath. That just killed any resemblance of consistency for me.
Anyways those are just my opinions, so if anyone feels like replying, i'm not stating any of this as a fact, this was just how i felt about the game personally.