It depends. Are Brave's ads more similar to the banner ads of the old days? If they are not so intrusive and privacy violating like modern ad-networks, that would still be a net win in my opinion.

As for the hypothetical youtuber, they are always free to put product ads directly in their videos if they can/want to. However, if they can only make money via abusive 3rd party trackers, that's on them.