Personal opinion? Fallout 4 wasn't bad. Wasn't as awesome as FNV, but it wasn't bad. What really killed it for me was the constant inclusion of the Creation Club crap. Had to keep waiting for F4SE updates just to get around CC nonsense.

i dont actually love vanilla fo4 but with mods (i have about 550 mods) this gae feels much better! fnv for me not that great, animations just feel wanky idk

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.

Since everyone else has already said what needed to be said about Fallout 4, I'll introduce another factor that affected modding for it.

On top of the abovementioned issues, I remember the creation kit for Fallout 4 being released a bit late. A lot of early mods were made using a technique involving TESnip (Do not use any mods made this way, they are known to cause issues). The other issue at the time was the release of Skyrim SE. A lot of people were more focused on trying to get their work migrated over from the original Skyrim. Which took attention away from Fallout 4 within the community.

Modding or FO4 is to a degree a pain, at times it can be cool and worth it when you see your project in-game and alive. It could become a buggy mess killing morale/motivation in other ways.
Another issue about FO4 is more down to scripting. Due to certain characters being so heavily scripted that he is needed to progress the actual campaign. Kind of also severely affects any other reasons to well mod. However, FO4 is helpful for other projects especially the F01, F02, FO3, FNV, F04, and F076.
Besides that though other games are more open sheets where possibilities can be done for your headcanon of course.

To be honest I always see Fallout 4 as a sort of test. They introduced a lot mechanics which I do enjoy such as the overhauls of power armor and the settlement system but they didn't seem to put as much care in. Like others have said the story was incredibly lacking and choices didn't have any weight which new vegas excelled in.