Whereas I hear what you say, I do not believe your “simple solution” will actually be that simple.
OK you have your Library in the cloud, but you need a Core to be running to access and play your Library content. Are you going to lug your Core machine around with you, because it sure won’t run on a mobile device? OK I expect you will come back with something like Roon must be running a multi-user Core in the cloud so all the heavy lifting will be done by some big server farm with the likes of AWS, and you just need the lightweight client to access and control it, and also receive the HiRes stream it delivers…
That is not so simple to implement and will cost, and although I believe Roon are looking into some form of Remote delivery, if it is like the model above, it must surely be a separate service, and separately charged for I would imagine.
I don’t think it is financially feasible for Roon to deliver such a service to all existing licence holders, although the annual fee could increase to cover - but then LOTS of “old Farts” just want to listen at home on their ancient big box HiFi rigs, so would not want to pay for this extra service. And as for delivering the new service to all Lifetime licence holders, Roon have to substantially increase their Capital and their Revenue costs without getting any additional income from them. That is a Bushiness model that cannot work financially, Generous - Yes; Feasible - No.
So it would have to be a separately charged for service; either as a stand alone separate product, or a Bolt-On to the existing service.
And it won’t be simple, which is why there is no other “someone” out there currently likely to pass them out any time soon, with a service that does what Roon does only better. It is a relatively limited market, Methinks.
So for me when away from home, I simply use the Tidal and Qobuz apps, which work, but do make me appreciate what Roon does for me at home. (Yes even us old has been’s listen to our music on the move or in other locations)…
If there were a Simple solution, someone would have done it (if they thought it financially worthwhile) but as there isn’t, Roon are safe for the time being. Look at the clout Amazon have, look at the massive development resources they have, then go see how poor their HiRes music delivery experience is…
I wish you well in your quest for music delivery nirvana, it is a goal we have in common.