You're right about the latency being a problem. I wouldn't touch Stadia but I believe many will and it's one more compromise people will accept in exchange for convenience.
Yeah, Google shuts off unpopular, unsuccesful projects. So what? Most of the ones listed are literally useless and/or outdated relics of the past which have been replaced by something better. Google is a business after all, not a charity. They don't want to maintain an useless project from 2005 written using who knows what technology stack.
If Stadia becomes mainstream and acquires a lot of users, they won't kill it off as it will be profitable. If it has an user count of 500 in two years, it will be gutted, why support an unprofitable product?
Nexus became pixel. Glass never left beta and is still an enterprise product.
The major differences are that Google is more involved with pixel hardware design than nexus (probably a good thing), and that pixels are more expensive (which follows the market price for flagship phones).
They both fill the niche of first-party flagship devices with the "pure, as google intended" (or something) android experience.