YouTube is not publicly accessible: they offer it under specific terms, namely that you watch ads or pay directly. If you don’t want to accept that deal you don’t have any more right to use their private property than you do to complain that the local movie theater wouldn’t let you sneak in when you didn’t like their ticket prices.

YouTube has no problem serving content to my yt-dlp client without ads, payment, authentication or terms of service.

That doesn’t mean it’s allowed, only that they haven’t blocked it again. You can’t use your neighbors’ pool without permission just because they don’t have a guard checking IDs, either.

Turns out, I can.

Up until they notice and decide to call the police.

I use an adblocker, call the police and tell them I told you so.

If you found people who make a habit of swimming in your pool without permission then I imagine you'd be the one calling the police.

Not legally, no. This thread is the lower stakes version of what happens when the owner gets tired of free loaders and starts enforcing their legal rights.