Most Japanese artists have a Pixiv or Nijie account. You should be able to move most of your follows to those services.
A lot are also jumping ship to misskey.io, which you can follow if you use mastodon/pleroma/misskey/etc.
I suspect the small amount of holdouts will soon create an alternative as well.
The few cents a creator gets from your youtube premium subscription is way more than they would ever get from you watching ads, so yes, OP is actually right.
Just because they’re not gonna get a massive cut from your sub doesn’t mean it’s not the most beneficial solution for everyone.