I don't think that's necessarily an unpopular opinion. Burton allowed his villains to chew the scenery, and so did Schumacher. We got what we expected with Jim Carrey.

I think most people's issue with Schumacher's Batman is that the extreme camp was a departure from Burton and not exactly what fans wanted from a Batman film at the time. The swashbuckling 70s Batman comics, and the dark, gritty 80s Batman had more than proven the character could be done seriously. Burton put that on screen with his two movies, which carved out a more modern, more gothic, and (for the time) more grounded Batman than previous adaptations. It worked, and people liked it.

Schumacher's movies reverted Batman back to the camp of the '60s, and was explicitly pulling from the Batman TV show, which was effectively a comedy more than anything else. Fans weren't feeling that anymore in the 90s, and they kind of still aren't (though I'd argue they've opened themselves up to camp a bit more after we've been to the extreme other end with Snyder).

That said, if there's one aspect of Batman that is always permitted to be campy, it's the villains (within reason). Jim Carrey's Riddler is basically Frank Gorshin's Riddler from the show, which was kind of the standard way of depicting Riddler for the era. It didn't align with what we generally expect from Batman nowadays, but it was undeniably entertaining, and not all together unfitting.