The only way to make YouTube even remotely tolerable is with liberal use of the "Not Interested" and "Don't Recommend Channel" functions.

I also set up separate YouTube viewing accounts by interest, so that I can clobber away everything not related to a specific interest in that particular account (eg. anything not sports related gets "Don't Recommend Channel"'d in my Sports YT account).

YouTube pretty much fights you tooth and nail the whole way, but eventually your blocking of irrelevant and garbage recommendations leaves them no choice but recommending things related to that interest.