Why even use the Sonos App? Apple Music via Airplay to Sonos works great.
I have to use the Sonos app because Music can only play via AirPlay to newer speakers. My older Play 1s and Play 5s, are not available speakers in Music when I make a selection--only my newer Sonos Ones, Moves and Roams are visible. And my speaker groups don't always include one of those newer speakers. Those older speakers can play via AirPlay, as long as one of the speakers in a group is a newer one, and is the lead speaker / first one selected in the group.
Technical question along these lines: if I do play music over AirPlay from my phone, is the phone the source, or is the speaker going to AppleMusic directly to get what I said I wanted to play? The Sonos app just tells the speakers what to go get, for example. The app doesn't pull the song down to my phone and then pump it to the speakers. My 19 Sonos speakers play background music the entire waking day, and my poor iPhone battery would be toast if the phone was the direct source, like in a BlueTooth-to-speaker configuration.
Also, in my family's use-case, we put on a long playlist (often an AppleMusic playlist) using the Sonos app and let it play all day. Let's say I am the one starting the music off, and then leave the house. The music plays on as instructed--the Sonos system doesn't even care that I left. Anyone else in the house can open the Sonos app and work with the running playlist (even if that AppleMusic playlist is not their playlist) and skip songs, etc. It is this functionality that opened my wallet and left kidney to Sonos the first time I saw a Sonos system in a friend's house ten years ago.
If we used the AppleMusic / AirPlay configuration in our house, and I leave the house with my phone while music is playing, the music is going to stop playing--unless someone tells me that the phone isn't the direct source, but only sends instructions to the speakers, and the speakers fetch the music. Also, in the AirPlay configuration, my phone is the only one that can control the music.
I am fortunate that the only problems I have with the latest issues is the clumsiness of the app--my system still works. And I truly feel your pain if you're one of the unlucky ones. Losing full functionality of my Sonos system and leaving my house crickets-silent, would we devastating: much like being up in an airplane, and all of a sudden the comforting and reassuring drone of the engines suddenly goes silent.