I mean, before Steam this was basically the state of gaming. No community, limited features, spotty performance. This is just teething issues. There is no reason a platform like Stadia can't work in the future as these things get better.
And, in terms of downloading gigs from afar, you're already doing that, but instead of being able to play games while downloading you have to wait to download 60gb of COD updates, consume your entire PS4 drive with a single game. And while that is happening, you're just sitting there not using your PS4 because opening another application pauses the download.
We are starting to see more cross platform support for games between PS4, XBO, and PC. But older games won't ever support cross platform between Windows, OSX, and *Nix. A browser port could easily change that.
> Why does "the web" try to recreate existing technologies and operating systems?
It's the same trend we've had since basically the dawn of computers. We move things into deeper abstraction layers. Why is this an issue in your opinion? Isn't more options better? Isn't ideal to adapt old concepts to new implementations? At the very least does it not provide potential educational value?