If there were more PC exclusive games that were truly GPU required monsters I could see the point of Stadia, but as time has progressed most AAA games that end up targeting PC usually have a generous minimum requirement threshold, and often its so generous that most things can actually do the job. The only place where the GPUs have been really required in the last few years is the VR stuff which because of general latency of input/response for Stadia would probably cause a lot more motion sickness in people than a local system. Stadia's benefit is capturing the kind of user that doesn't care about quality (because if you did you'd just buy that tower), but those are the kind of users that would make do with what they already had anyway for cheap.
In my opinion this feels like the same slow death as OnLive, with even less benefit in knowing that OnLive's entire focus was on streaming gaming rather than Google who would put this product on ice in 3 years.