I believe Stadia's problem is not their tech, but rather their business model.
Not just business model, but their communication and strategy too. Google seem to have rolled up assuming that good tech and being Google would be enough to muscle in to the gaming space. They didn't even found a single studio until around the time the service launched, at a time when their ostensible rivals (who were already entrenched in the market) were shelling out hundreds of millions if not billions on their content pipelines - or were going another way like nVidia, and simply facilitating access to games you already owned.
Google wanted the lucrative sales/accessories cut that comes with being a platform holder, without making the investments to actually be a viable competing platform. And worse than that, since they didn't have any studios that also meant they didn't have any game to point to in order to show what "the cloud" could offer to their games that they couldn't get elsewhere - all of the magic of the cloud was purely theoretical talk. Their big "launch title" was an expansion for Destiny 2, and Gylt... and indie game.
Then they launched the service so the only way you could initially get in (aside from an invite from someone else) was to buy one of their $100+ founder/premiere kits, completely nullifying one of it's potential advantages - the lack of an upfront "buy-in" cost/effort like with consoles. And they were doing this late in the last generation, when people could get an entire console for less than twice that amount. Then months later they eventually removed that requirement, but they did so quietly and with zero fanfare after the service had been kinda laughed at and forgotten.
They also made the baffling choice to launch the service in a barebones state, to where you even needed a browser just to buy games because the Stadia UX itself didn't support it. This ensured poor reviews, and kneecapped it right off the blocks.
They eventually got off their asses and signed a deal or two with Ubisoft and EA to ensure at least some of their games came to the service on their release date, but this was too little and far too late. The EA deal literally came just before they closed all of their studios and started exploring commoditizing the Stadia tech stack instead.
So yeah - they nailed the basic streaming technology of Stadia. And they tripped on their own dicks when it came to LITERALLY EVERYTHING ELSE. Some people like and use the service, but some people like and use every service whether it's considered a business failure or not. Some people liked and used OnLive and Gaikai.