and with the most popular games in the world right now being twitchy competitive shooters I don't think the best case scenario 100ms input delay is going to be acceptable, even half that is going to be awful for mouse input.
Not input lag, but people already put up with bullshitty gameplay like this due to internet latency issues on games with larger amount of players :
I don't believe the large masses playing those so-called 'twitchy' games are highly judgemental with that sort of thing. If anything, Stradia, while introducing a form of input latency for everyone, would have the potential to make what you see on the screen be closer to what actually happens by running everything, server and player clients, in a LAN.
Most of the popular online shooters have dogshit hit detection. The closest thing to acceptable among the mainstream games is CS:GO but that game has other issues of its own.
Heck need I remind you one of the most popular FPS series, the CoD, had PEER TO PEER hosting rather than dedicated servers? Same for Halo. Some of the CoD started going back to dedicated servers but basically the only people who care enough to make it a breaking issue is a fraction of the PC user base, and console gamers never cared. If you ever gave a try playing a P2P style FPS I can guarantee the latency issues felt during the game that break hit detection are worse than anything game streaming services like GFNow introduce to your input lag.
You are vastly overestimating the segment of gamers who care. Online shooters have long lost any semblance of being truly competitive since arena shooters died.
Games like Fortnite, Titanfall, CoD or Battlefield are not the paragon of what would be impossible to market on these things. At best 10% of their playerbase would bitch and the rest would still play it there.
I used to play online shooters, I don't even care about them anymore. The genre lost me aeons ago and it's not streaming that killed it.