(Whether or not you're playing multiplayer isn't really relevant, because those other people are talking to the datacenter, not your local client)
> You may have other issues going on? I don't know why you're getting 500 millisecond delays. I'm certainly not getting that.
I haven't personally tried Stadia, and 500ms wasn't intended as a representative example, it was just an extreme number for the sake of illustration.
I have, though, read reports from lots of people who have "good" internet connections, saying Stadia is noticeably laggy (just look at the top comment on this very post).
To get down to specifics, a latency of >16ms is a lagged frame at 60FPS (which is the standard expectation for the current gen of consoles, and has been the expectation on PC for many years). That time window also has to include actually processing and rendering the game state (you can throw hardware at this part, but only up to a point).
So, that Starlink figure of 40ms will still give you a pretty unideal experience.