Most of those things you describe you can do with Airplay and the RemoteApp. That does break down with Spotify and Google Play.The nice thing about not using AirPlay is that you can use your device for other things at the same time as the music is playing. Let's say you AirPlay from your phone to some other speaker. What happens when your phone rings? Or what happens if you open a video app on your phone and want to look at a video, but other people in your house still want to listen to the music that was playing?
With Sonos, the app is used to control the music, and that's it. It doesn't have to stream anything from the phone to the speakers. If you really want to stream something from you iPhone music library, you do have the option using the app, but why would you want to? Sonos can use your online Apple Music library, your local iTunes library, Spotify, Google Play Music, and other sources.
With one of the recent updates, you can even control the music from your iPhone or iPad lock screen, just as if you were using AirPlay.
It's a great system, I just wish it didn't cost so much so that I could add more zones to my house.
It does sound to me like the main advantage of Sonos is that it isn't tied to a single ecosystem like AirPlay is to Apple/iTunes. I stopped using Pandora/Spotify when iTunes Music was released and have been very happy "locked in."
It seams like you are paying quite a premium with Sonos for very little added benefits, but that is just my impression.