I’ve played input-sensitive games with friends on GeForce Now for several months at this point — no major issues with lag.
I’m not really a casual gamer either. I’m still surprised that GeForce now doesn’t have an app for Linux. I switch to my Mac laptop to play stuff like Fortnite.
Fortnite is about as casual as it gets. You won't rank very high in a twitch shooter like CS:GO (or keep consistent ranking) using a cloud gaming service.
Just because one game has guns doesn’t make it less ‘casual’, which btw is a dismissive word to use in the context. Why are ‘twitch reactions’ less ‘casual’ than puzzle solving?
Plus cross platform.
50ms of input lag on the other hand is very easily noticeable. And makes games unplayable for lots of people.