People don't like the creator of Brave because he's supposedly anti-trans. He donated to some anti-trans political group iirc.

The browser also has some crypto stuff (web advertisment replacement, block chain based decentralized browser sync), and a lot of people hate crypto these days.

Personally I think it's a good browser, the web needs advertising revenue to function and it's solution to replacing web ads with optional browser ads that still pay the websites you visit seems like a decent solution. I respect the push to use a non-chromium browser, but personally I rely too much on browser tab groups to use anything Firefox based.