There are plenty of timestamping services out there, both blockchain-based and otherwise. If a video creator timestamps their video as soon as they create, and before they upload it, it could prove definitively these kinds of fraudulent claims.

Also, these services are usually reasonably priced, and sometimes even free, so it would be reasonable to use even if you're making several videos a day.

Raw takes including stuff that was edited out of the uploaded video seem like a simple way for many types of video.

I think the real problem is that evaluating such proof would need to be done by a human, and YouTube want a completely automated system.

Register a hash of the (video + your name) on blockchain, that's the proof that you had it first.

Just needs a nice UI, and, well, Google giving a damn about it.