Google Play Music happens to be absolutely perfect for my usage (including the ability to upload my own tracks AND stream them). I'm extremely annoyed they are killing it off as I've tried everything else and it just doesn't work for me. The replacement YouTube Music is... abysmal. Well IMO anyway.
Only pointing this out because it speaks to your point. I think you're spot-on that APIs and embracing 3rd-party clients are the way forward. Not just for music, but any service where the primary UI challenge is making everyone happy (hint: a lot of services). I'd instantly support and switch to a service like GPM that put APIs first, assuming all the same back end functionality and catalog was available. Even if the "official" client didn't suit my needs.
Only pointing this out because it speaks to your point. I think you're spot-on that APIs and embracing 3rd-party clients are the way forward. Not just for music, but any service where the primary UI challenge is making everyone happy (hint: a lot of services). I'd instantly support and switch to a service like GPM that put APIs first, assuming all the same back end functionality and catalog was available. Even if the "official" client didn't suit my needs.