the content creator isn't following the proper system then. You don't need YouTube to do a copyright/IP violation claim. Google is actually opening themselves up to significantly hot water if they are indeed refusing to allow a process for DMCA on creators that are deleted off the platform, as there are severe penalties for not reacting to a DMCA claim when you are a content provider.
If they actually owned the rights to the videos, that creators first step when learning that Youtube is not going to do anything about the violation, is to manually file it themselves, and honestly they should state that Youtube at that point is intentionally allowing it which would perhaps pull Youtube into it as well
just because YouTube decides that they aren't going to do anything, doesn't invalidate your claim to copyright. I'm surprised that the channel hasn't seeked legal action against anyone regarding it.
My two cents on the matter is that it's likely the channel is worried that their videos aren't transformative enough fair use wise and that they themselves may get into legal troubles if they attempted to. A lot of commentary artists stay borderline on fair-use and not fair use, however if this was not the case, they have a pretty decent chance of winning that suit.