I'm grateful for this thread because this move absolutely destroyed my last bit of good will towards Google. I'm incensed over it. The YT Music app is so much worse an experience, it is acutely evident users are not what Google has in mind with this app. Just embarrassingly bad, as has been noted by many others here.
For the users who stay using the undeniably worse app, Google will see more views for yt videos, upping their vanity metrics there. The addition of ads playing on music that I brought to the app in the base edition is awful, but good for the bottom line of the ads group.
Meanwhile, thanks to this horseshit, I am [finally] pulling my personal domain off of their G-suite, my next phone is going to be an iPhone [or a Librem], and I'm going to offer my services free to any of the clients I've put on to G-suite [several dozen over the years, regrettably] who want to egress somewhere safer.
Youtube is inescapable for video and I will likely always use it. But I'm going to stop paying for ad free and find other ways to get what I want from Google without giving them anything in return.
I'll also do everything in my power to try to make the ill will this has generated into a chorus.