I'm a streaming believer, but the way Stadia is being marketed and sold is a mess.
The trouble with Stadia is that it doesn't have first-mover advantage, and nether is it a fascinating engineering challenge that Google's engineers have solved ahead of anyone else - which is the kind of stuff they're actually good at selling.
If you think about it, Google's most-used consumer services were all either first or near-first (Gmail and Android), or they represented such potent engineering progress that they basically sold themselves - i.e. search, Maps, and Photos. Stadia is neither of these things. There are at least three (soon to be four) viable game streaming platforms that already have apps for a variety of different devices. And the actual technical portion of game streaming is as good as solved already, bar some refinement for input processing and latency reduction.
This puts Google in a position I don't think they've ever thrived in: they're doing something several people have already done, entering an entrenched market with no prior experience, and they can't even say they're doing anything that unique, technically speaking. I believe this is why the messaging around Stadia is so muddled: it's not doing anything new. I think this is also why you get Google engineers talking about things like using machine learning to predict inputs to achieve "negative latency," because that's just the kind of mode Google is comfortable talking in, so they fall back to it when they don't have anything else to say.
And when Google did get creative and start touting the cross-device benefits of Stadia, it then turned out it won't work on most smartphones, and its wireless controller won't be wireless. So that was hardly a marketing coup.
Couple all this to the fact that Stadia - unlike PSNow or GeForce Now or Shadow, or XCloud when it launches - is also launching with an entirely new ecosystem, with a new storefront, new friends lists, and the need to port games to a new fixed platform.
I'd love for one of the existing streaming services to really hit the mainstream soon, but Stadia just has far too steep a hill to climb - especially when you consider that Google seem to have no idea how to actually push it up there.