It's personal preference for me, but having played almost every D&D CRPG in the past, from the previous Baldur's Gate entries to Icewind Dale and Neverwinter (and even the old "gold box" AD&D titles such as Pool of Radiance), I've found that I am bored and sick and tired of Illithids whenever they show up. They don't do anything for me and games that have them as a plot point have often been a tiresome slog where I have to get past the part with them in it before I can start having fun again.
For me it's a WOTC/Hasbro property flex they seem to need to keep flexing over and over again because they own it and so I was hoping BG3 had stories and settings and maps that don't feature yet more psionic slavery brainvore fuckery.
That's making me hesitate about my purchase, because I don't know how much of it to expect but the trailers and basic plot pitch on Steam made me worry. 
spoilers for act 1
the game starts with a mindflayer putting a psionic parasite in your eye in order to turn you into a mindflayer. it adds some dialogue options but you dont have to use them and i think there's a parasite skill tree if you interact with it a bunch. im not sure how the rest of the game is going to go (im only partially through act 1) but yeah it seems like mindflayers play a pretty big role in the main story, im guessing that they'll feature prominently in the later stages of the game and will probably be the big boss battle at the end. at the moment my party's main quest is about trying to find a cure for the parasite but there's also a bunch of cool side story stuff going on. each of the origin characters has their own fleshed out backstory too.
Thank you for the information.
I'm still on the fence about buying the game; I enjoyed the two Pathfinder games (Kingmaker and Wrath of the Righteous) but if BG3 is just "sort of that, but with a lot of added proprietary WOTC Mind Flayers(tm) and maybe some visually assisted
" I'm not sure if I should.
Take it for a test drive. Our lady fitgirl is working on a repack.