I grew up with cats and I never had any problems with them as a kid, or at least none that I didn't pin onto stupid adults instead of the cat. I didn't really like stepping on litter, or having to stand 2 feet away from my bathroom sink to wash my hands since there was a pee pad there, or getting cat hair on my "it was clean just 1 second ago" legs after stepping out of the shower since the cat was perpetually locked in my bathroom . . . But I didn't hate the animal for it back then.
It was mostly my adult experiences. I just kind of randomly decided one day that I liked not getting fur on my belongings once I lived in a petfree house for a few weeks, and cats just so happened to be the animal that continued to cause issues. My housemates wanted a cat and there was no no-pets clause in the lease, so they just kinda ignored my opinion. And that was fine until I came back from a 3-week trip and the cat just pretended I didn't exist even though "we'd been very good friends" before. I was upset and figured I could ignore it; that was fine until we moved into a small apartment and there was not enough space for the animal. Also it now was destroying blinds by jumping into windows, which woke me with already awful insomnia up . . . And litter was constantly on the bathroom floor since the owner (who was my partner) decided keeping the litterbox in his room was an awful idea because something something carpet . . . And I was hurting my knees trying to step around it all the time, so I just started walking straight into it instead. Talk of rehoming the cat happened, and I had to endure the experience of 1. My partner CLAIMING he would choose me over a cat, 2 my partner ACTUALLY choosing to keep the cat and also his mother gossiping about me behind my back. Then I had to deal with living with this animal whilist knowing that despite doing housework, cooking, having paychecks, and overall being more useful than a cat . . . we would never be on even playing field and it'd just outcompete me. This went on for a couple years until we rehomed it, the reason being because "I was a danger to the animal". However you wanna rationalize it, buddy.
There's like . . . Other reasons I could site, such as "they are a drain on your wallet (and the ecosystem) for no real benefit since pets are useless; rather than getting a dependent make a self-sustaining friend or get a stuffed animal"
But really, it's just a visceral emotional reaction after having to deal with negative experiences that only happened because a cat existed. Like, I'm sure I'd hate dogs instead if this happened with a dog instead of a cat . . . Now I'm just adamantly petfree, not interested in future relationships anymore, and cats have extra baggage.
They also remind me a little bit too much of my failure to make secure social connections. A friend once said that his cat was non-negotiable, but I've never once felt that way about somebody else (or that I was that to somebody). I see a lot of myself in them and it's kind of painful. I don't need another me in my life.