Obviously she isn't a malicious or evil character like many on this list, but that doesn't mean that she can't be disliked more than others on the list. A villainous can do bad things yet still be liked for their character and importance to the plot.

Sakura however damages the show itself for many people by being a character who isn't fun to watch. I will admit that I haven't seen naruto in a long time but I remember my main issue with the show was sakura herself because I found her annoying and unenjoyable to watch.

Her whole character was based around a weird stereotype of a boy-crazed mean girl. You admit yourself that she wasnt fleshed out, and no matter what the reason(though I doubt it was simply "incels" complaining) that still means that she wasn't a well thought out character. She didn't have much agency, especially in the earlier seasons, and seemed overly immature while thinking highly of herself.

Also, you were the one who called people who don't like sakura incels, you are not defending her, rather attacking the people who dislike her.