Stadia is also an upgrade to a last-gen dedicated games console, a PS4 or an Xbox One. Just look at the recent Cyberpunk 2077 release which ran fine in Stadia, but struggled on those consoles. With the current-gen just releases, plenty of people have not yet upgraded.

Strictly console-wise Stadia is an upgrade to those last-gen consoles. But they really need to get more games on the service because that's what people are there for.