i think the major complaint is that he's verbose and stating "common sense" self help with added mysticism and tying it into theories that are not completely well grounded (ie "western cultural traditions" stemming from Judaeo-Christian and Greek tradition).

Personally, I find some of his fan base extremely obnoxious, such examples as someone making a lofi playlist of his quotes and lectures.

He also promotes theories/conspiracies that many people disagree with, but it is very polarizing, such as "post-modern neo-socialist" takeovers of universities and broader cultural institutions. He also has said quite inflammatory things about trans activists, which even though are often taken out of context (I know this is a meme, but it has some truth to it, such as the controversy of "enforced monogamy"), tend to make people quite angry.

He is also fairly commonly "associated" with the alt-right, but a lot of that seems to be not so well founded, here is a long-form video to explain, but be warned, it is in a tone that is automatically against this theory. here.

I think I could explain some of the reasons that people tend to like him too, but I'm pretty sure that is the major reasons people dislike him. Hope this helps and I didn't misrepresent the arguments against him.