Stadia had (has?) free games each month that remain on your account as long as you're subscribed. So in that way, it is. It just doesn't provide the huge library that XBGP does.
The monthly fee was for 4k and other features that weren't necessary. You could stream anything you bought on Stadia for free at 1080p, no subscription.
It was like buying a game and getting a console for free, but with an optional upcharge for an even better console.
The marketing for all this was horrible. People still don't understand what Stadia was and wasn't. And the launch was limited to people willing to spend $130 for the custom hardware.
That hardware wasn't necessary. They just decided to do that at launch as a way to milk some gamers of their money in return for early access.
But again, the marketing was horrible. And the free access came many months later. For a system that it's best feature was the free streaming access, they completely destroyed it at launch.
And of course, as everyone pointed out back then, Google doesn't support the things they create unless they're related to advertising somehow. And they've already shut down all the studios they created to make games for Stadia.
And the big "wow" feature that they kept advertising, "negative latency", never got released. Many thought it was already in it, so the latency that Stadia has was very disappointing compared to the hype that Google gave it.
It's just a disaster from start to finish, marketing-wise.