I still think Google made the right decisions for a long term play. People are upset about the idea of "buying" a stream. But the same concerns were (are still) raised with digital, and ultimately trust over time + convenience wins out. The idea of Stadia (in theory) instantly playing your library of games 20 years from now is pretty attractive compared to every other platform including PC.
There is a concern that Stadia is a new platform rather than piggybacking on an existing developer target. This is a clear hurdle, but the industry favoring big middleware like Unreal Engine, and cross platform technologies like Vulkan mitigates that a lot. Also the prevalence of Linux in all kinds of spaces means it's far from alien to most developers. Most software engineers prefer linux/unix to Windows already. Over the long term, it's more important that the first party (Google) can actually control their platform rather than be limited by the technical and licensing terms of a core vendor (Microsoft).
Right now Stadia is a pretty bad platform. The library has some bangers, but nothing setting it apart. The system-wide innovations possible with streaming are mostly not implemented. One major use case I want to see is simply texting a url to a friend and instantly playing multiplayer with them. This isn't available yet, and there are few games where I'd do it anyway.
Another major problem is the free to play model. Widely played games like Call of Duty Warzone and Fortnite are not on the platform. If they were on the platform, they'd be locked behind the Pro plan (per PUBG). Google has to figure out a model where free to play games can be actually free to the user, or they're going to miss a huge opportunity. I know plenty of people who would stream Warzone just to never bother with 10+GB updates and shader installs.
The other thing of course is exclusives. Stadia has got to roll out a world class first party. It's a big job, but it's the price of admission.