Kai Winn is intended to be hated. And Dukat is such an enjoyable character that the writers had to go out of their way to remind everyone that he’s a bad guy.
I don’t think people hate Wesley in the same way. They don’t hate the fictional person, they hate the way the story presents him. They hate the way he saves the ship by being effortlessly superior to everyone, including Data. And it doesn’t help that he was a young actor with limited skill, featured most prominently during the shows weakest seasons that suffered from bad writing.
I think there’s far less negative reaction to the Wesley we see in The Samaritan Snare or The First Duty. He’s still a smart kid with a lot of potential, but the story presents him as a flawed, vulnerable person, rather than an obnoxious little shit with a terminal case of smug overconfidence.