A creator can have up to three strikes, with them disappearing over the course of time if they don't get more strikes. Contested copyright strikes may be elevated to DMCA requests if YouTube finds in favor of the creator, but it's not required.
If you run out of those strikes, your channel is immediately shut down. It's possible (especially with a large backlog of videos) to exceed this strike count before you can use their tools to argue against the strikes. When this happens, your account is shut down, and a "grace" timer is enabled to allow you to try and challenge the copyright strikes (one at a time). If that grace period passes and you're still out of strikes (don't dare to take a vacation), the only remaining choice is to appeal to the public.
No DMCA claims necessary.
Youtube does allow DMCA counter claims because they legally have to. Youtube has absolutely no wiggle room with DMCA. No amount of complaining to them can ever change that, either. You have to get the laws changed.
Do you understand that the content in the submission is infringing? And not just to the civil level but to the criminal level? And so YouTube losing safe harbor would be huge.
No, it wouldn't, because YouTube is actually removing the content. So they're not going to get sued for infringement, and other parts of the DMCA still protect them even when they operate outside the bounds of the takedown notice procedure.
> there are other extra jurisdictional mechanisms that Google employ to make your life difficult as a creator.
That's not quite true. The DMCA is a very strict mechanism. You get a notice, you take down the content, and if the uploader isn't happy with that, they have to sue the claimant.
Of course, Youtubes process is streamlined for its own interests and the interests of big corporate copyright hoarders. But it's not designed to bully creators.
The problem isn't really the process in itself, it's how Google applies it and the fact that Youtube doesn't seem to care that much for its creators.