The increase appears to be dramatic. I signed up for YouTube Premium long ago simply because I couldn't stand the occasional ad anymore. I recently was at a friend's, and I wanted to show him a particular cooking video that I liked, on his iPad. It was a 16-minute video and it was interrupted three times by an ad. mid-video. Unbearable.
The thing is, through Premium, I was actually looking forward to discovering new music with the YouTube Music app. Was I wrong. The recommendations are crap. They are repetitive to the point of nausea. I have a few hundred "liked" songs, but the recommendations are heavily skewed towards a few, mostly recently "liked" songs.
This has actually lead to me dreading marking a song as "liked", as it inevitably leads to this repetition and, much worse, to unending recommendations of the same artist's other songs, even if I "dislike" every. single. one. of. them.