Do you legitimately think that any use of the words "what about" makes something whataboutism?

No, that’s not what makes it whataboutism. That’s just a funny bit of your comment. What makes it whataboutism is your continued insistence that the problematic behavior is sourced from elsewhere. That’s not how things work. The right-wing extremism on Steam isn’t a symptom of extremism elsewhere. It isn’t sourced from elsewhere. It’s there on Steam, because the source for it is the same on Steam as it is on Twitter, right-wing extremist users. Suggesting that it is derived from the other sites implies that Valve is less responsible for it than other sites, which doesn’t make any sense. Furthermore, your argument in your comment is based on your perception of victimhood of video games by other media, which isn’t relevant to the conversation at all.

And finally, the fact that Steam supposedly has, by your estimation and without any supporting evidence, less right-wing extremism than other sites doesn’t make the problem better or worse for Valve. It’s still a problem, and it’s one they have to deal with. Not twitter, not Facebook, and not anyone else.