You've found quite the hornets nest, it seems.

I pay for premium because YouTube does video delivery better than anyone else in the world, and it's not free for them to provide. Lots of things to hate about YouTube/Alphabet, but theft is a corrupt way of expressing discontentment.

Also, if I pay for premium, then content creators get paid, and I don't have to shell out for merch to not feel like a terrible person.

This is true. The selection from YTMusic is likely unparalleled, because (afaik) as long as a song has been uploaded to yt, it's available through the YTMusic portal. I definitely have my complaints, but all in all I'm happy with it.

Ngl, I feel pretty smug about migrating to YTMusic last month.

The app is a worse experience than Spotify's (shocking that it's possible), but I already pay for YouTube premium, so YTMusic is basically free for me.

Also, you can't download songs on the desktop client (I have metered, spotty wifi, so this actually matters to me) and there are no first party tools to migrate playlists/likes between streaming services (not a yt problem, but an industry problem).