These 80ms were just fine because game engines already employ a lot of nifty tricks to minimize the negative impact of latency. Tricks which mostly only work as well as they do because the engine has an inside view on the gamestate. 80ms of video lag are far worse for the gaming experience than 80ms of "conventional" client-server lag.

Try to track a moving target when your screen updates almost 0.1 seconds after you adjust your joystick.

I expect Stadia input latency to be much greater than that, though, because most display hardware adds at least 30ms on top of whatever latency Stadia introduces.