People in general don't like it because they like quick games with a bunch of tactical moves that lead to more "excitement". Even grandmasters do not like the somewhat rehearsed and "slow" nature of the queen pawn openings. E4 is relatively close in terms of success and the sicilian leads to a lot of quick tactical play.
Also, many novice players try to pretend not to like it because they lack the ability to win mates in the positional sense and instead attempt to get a quick tactical mate with a lot of attacks and exchanges.
Finally, closed games (queen pawn has many closed positions, except for the Indian defenses) lead to a lot less flexibility, and flexibility is a lot of the fun in chess.
Nevertheless, d4 is an excellent opening (probably the best, besides possibly retí.
I always hear people ranting, "It's not tactical, it doesn't help you get better, it's boring, it's positional and positional play doesn't matter at beginner level, etc."
I am estimated 1200 - 1300 USCF, so I know I don't sound very reliable! But, I don't see what's wrong with playing positionally. I like positional play better than tactical play. Positional play is more interesting and fun. It's also great to fight for a spacial advantage to a point your opponent is crammed in and eventually has to resign the game.
But for some reason, people hear keep hating on "d4" and I really don't see why?