You can make smart playlists- but you might have to do that on the Mac. Smart playlists collect songs by whatever criteria you want- say music you hearted from the 90s added in the last 6 months. You can go wild with custom selectors and they’re live updating. Those lists get synced to all your devices. Playlists can be nested in folders- again you might have to do that on the Mac side. I’m not sure in iOS you can move contents of folders or lists into each other but on the Mac it’s drag’n’drop. I do wish iOS music app had a mechanism for creating and adjusting the smart lists though, because they’re great.
The limited support for Smart Lists might be my biggest gripe for iOS. Yea, Music can use them, but you can’t create them. And Photos on iOS doesn’t support them at all.
It's an unfortunate situation, but there's an app called 'Miximum' that I use to create a smart playlist for all of my "Loved" songs. Also works really well to make genre/decade specific playlists if you've got a large library
Unfortunately I found that AM did a very poor job of generating an enjoyable personal radio from my “liked” (added to library) songs.
Really wanted to use it, and I tried for about 6 months, but I ended up going back to Spotify. First day going back to Spotify made me even more disappointed in AM because of how spot-on the music discovery is there.