Good Point:
The gameplay is somehow unique.
There is many mod that has good art and mechanic.
Some people make a mod of other game/story/meme and make them revive from being dead. (EX: Indie Cross, Sonic.exe)
Most of the mod and original game has good instrumental.
Bad Point:
If someone not interested of the song that has only leitmotifs (or feel normal with leitmotifs but not ok with character made the noise as leitmotifs) might not love the game.
Some mod just made by people that be like "OMG!!! MY MODS IS THE HARDEST!1!1!" (But some of it is also make it's for meme too) which is uh kinda cringe for me (and most of it has the vocal/notes that is break my ears and somehow it's popular).
Some community of FNF is very toxic (Depends on what mod it's too).
There is many (FNF/FNF Characters) video in youtube that is... cursed.