"Toxic boys club" sums up a lot of the historical problems, but a quick Google of "riot games culture problems" will give you literally dozens of articles to read.
I have work with a few ex rioters and have interviewed a few (at the time) current ones, and have heard personal confirmation of many of these problems. It's a big company though, so some departments are better or worse in this respect.
But yeah, it's not really a great place to emulate if you're trying to build a healthy culture, at least IMO.