Well apart from one or two first party games, Gamepass games are only the base game, no dlc's etc. And wasnt it soemthing like 70% of all gaming revenue last year was for DLC and MTX? ,it was somethinglike that.That's sort of how I hope subscription services go. Big AAA games are paid releases that after some time come to the subscription service.
Still don't see how the model is sustainable otherwise unless you turn all your big AAA titles into microtransaction fueled GaaS, or significantly raise the subscription price.
The potential waith people buyilng mtx abnd dlc on Gamepass titles is huge, especially when they are getting the base game for 'free'
And also, and somehting people always fial to mention, Gamepass is also a store front where you can buy games. Buy games with a permanant 20% discount too.