What was impossible about OnLive? Using the app was an impressively responsive remote desktop experience, and cloud gaming is very much a viable reality as shown by PlayStation Now and GeForce NOW.

I agree. From what I read about OnLive's failure, they had major problems with founder Steve Perlman, which spiraled into lack of direction, a pivot, and a crash. The tech worked pretty well when I tried it.

Getting a comparable user experience. The technology is impressive but the video quality, FPS, and latency are not. Most people are just surprised it even works as well as it does, but once the honeymoon period is over the issues start to become apparent.

This is why you mostly hear stories like "Oh, I tried [service] out once and it was actually pretty good"; it's a novelty for most and not worth paying for.

I played a bit on OnLive, just to test it out and I thought the experience was decent enough on my (at the time) MacBook Air. Perhaps not good enough for twitch multiplayer gaming (I didn't try that), but I thought it was ok for the single player games that I tried.