I subscribed to Google Play Music All-Access for years and wouldn't have cancelled[1] if not for regional pricing making Spotify half the price. The music selection was far greater than Spotify and the like, I could upload and match my purchases elsewhere, and their radio algorithm was actually really good. (I sorely miss it after using Spotify's)

But YouTube Music is just a mess. I migrated my library to YTM and my experience is like the rest, but worse:

* You can't migrate to brand (aka alias) accounts. All of my likes, uploads, favorites, recommendation profile are on my alias but to listen to my music I have to switch to my real name account. Oh, but aliases can still use YT Music, so there's virtually no reason for this restriction.

* Switching accounts is for both YT and YT Music. So if I switch back to my alias on [normal] YT, the already-open YT Music tab will stop the music and ask me to switch back or refresh.

* All of my music poured into "Liked Videos". Except only about ~180 songs are there and I had over a thousand saved, if not thousands. No idea where the rest are.

* Some of the songs are "not available in your country" but if I search for it and find the official music video, that one is.

* This applied to GPM too, but: no desktop app. You can pretend the web app is a desktop app (and it's a little smoother than GPM at least) but it's still much more taxing than even a webview app like Spotify's.

[1] Fun fact: if you unsubscribe from GPM All-Access, your liked/saved songs that aren't uploaded disappear but are still in the DB, so you can't even see them. I don't know if they're part of Google Takeout, but when I moved to Spotify that meant I had to remember what songs I liked.