not sure what your point is. let's assume it's true. That still means the ads are paying for YouTube to host the videos. Without that those channels would have to pay for hosting themselves and could not afford to make the content.
Further, most of them would have never even tried if it wasn't free to start
Then, I don't buy your premise. Most of the channels I watch insert ads directly for Brilliant, NordVPN, etc... which means even without YouTube's ads they're still ad driven