I am not saying JRiver should be a streaming company. But spotify, google, apple music, these aren't going away anytime soon, and if they are, everything indicates a new streaming company will take over, whether they make money or not. It is in this reality MC must operate, the reality where streaming is popular amoung the music-listening and video-watching public.
This is why I think the solution is to get the audio from these streaming apps into Media Center, rather than JRiver building in custom support for each service.
Developing custom support for individual streaming services seems to be an increasingly bad idea from a business perspective unless you're a company the scale of Sonos, as there seems to be one or two new services launching every year, these streaming companies often seem to update/change their APIs in ways that breaks the service every few months, requiring additional work, and most companies seem to cut off their APIs after a year or two if they get big enough to not have gone out of business by then.
With iOS it seems relatively easy to get the audio from each service's app into Media Center, as you can stream AirPlay to a PC-based receiver and forward the audio to MC via the WDM Driver.
I don't know if Android has that capability built in though, or what standard they're using for that - if any.
The only thing which seems to complicate matters there, is being able to route the WDM input to your desired speaker output easily.
The WDM driver has a few issues right now
such as stalling, and there's no convenient way I can see to direct WDM Audio to a specific zone.
To do that would probably require JRiver to develop their own AirPlay receiver, so that each Zone shows up as a unique AirPlay device - and that's something they have said won't be happening.
The next best thing would be an easy way to quickly route WDM Audio to a zone of your choice - which I guess could perhaps be done by playing WDM Audio to its own zone, and then linking that to your desired output on-the-fly, but that means you are jumping between apps (the streaming app and JRemote) which quickly becomes a nuisance if it's something you are going to be doing a lot.