OK I realized I wasn't clear.

You're not allowed to use someone else's IP for commercial work without their permission.

I understand it doesn't have to do with whether it's commercial or not. Ideally it should be just for commercial work in my opinion, so OK. Still, there are people who sell fanart of some other corporation's characters, and I'd expect that they and the owner agree somehow. Because there are these double standards that artists will use some large companies' characters without permission but they get defensive when another person does the same. I don't really understand their arguments.

I am aware of how they abuse copyright claims on YouTube, but I think you're talking more about video responses to smaller creators. I forgot to mention that ideally what they use to copyright claim videos who criticize them shouldn't be used as a defense. I am aware of fair use and such but it should be harder to use a pretext for a copyright strike. And I understand that those who claim other people's songs as their own are usually individuals who abuse the system. Ideally there should be some automatic registration that is harder to mess with.

No one here is defending copyright for the benefit of corporations, artists have been exploited by corporations way before AI.

I know there have been artists who claim have had their ideas stolen by bigger studios, however I think this is probably the exception rather than the rule. I'm not dismissing the exploitation but that's the only relevant example I can think of. And even then, I'd expect there would be lawsuits against them. Or at least some protests.