FreeTube and other front-end replacements exist. Could they turn them off? Sure, with a bit of work.

Though so long as it is a public service (responds to the public) that does not require an account to watch videos ... they will only ever be able to annoy people. It's the same problem as piracy. It's a question of convenience, and if they make the main road a less good experience than the stripped down one... They're only hurting themselves.

If Google had half a brain, they would've embedded the ads in the video streams years ago. Instead, they "innovate" by making the entire internet worse.

(yes I know ublock blocks A LOT more than YouTube ads, and Google's revenue is all their ads, but YouTube is a perfect microcosm of why Google is the wrong company to solve this problem)