I'm not sure this was an 'obvious failure of execution'. They wanted to build a gaming cloud-streaming-only service, and they built one. I don't think you can build a better one because the problems with cloud-streamed gaming are with the concept not execution. The streaming service provided by Xbox is on par with Stadia, in that it suffers from the same latency, and graphical downscaling issues as Stadia did. On the Xbox it is part of my subscription (so technically 'free') and I don't want to use it because the experience is bad (although it is nice to quickly sample a game without needing to wait for download and install).