I've googled the situation regarding YouTube, and the proliferation of ads is unfortunately their stated intention.
In so many words, they say they intend to monetize their videos to the hilt, regardless of their content or what the agreement between certain uploaders and YouTube may be. I might not have that entirely right, but the situation right now is reprehensible for the number and frequency of ads, and just plain stupifying for their sometimes bizarre content, as BK notes.
I'm finding varying degrees of success in avoiding the ads on different platforms. Whatever protection is built into the MacBook and Safari, I believe I'm not getting many ads there. I've also downloaded and installed a "content blocker" on the iPads (the old one and the Pro), and the phone, even though I hardly ever watch videos there.
But on these I'm definitely seeing way fewer ads now, and one sign that something is at work is my having to hit the "play" button on certain videos because they no longer start automatically. I can deal with that. I'm a devout user of ad blockers, anyway. I allow as little of that noise into my life as I can.
EDIT: The blocker I'm trying is AdLock from the app store.