As many other topics in this forum, gamepass praise is a bit on the exaggerated side imo.
Don't get me wrong, it is a good service that has an audience, and more options are welcome.
But let's be realistic, so far the service has been constantly on promotion so value is obviously better than if it was full price.
At full price things change quite a bit: yes first party is there day one, but today's MS first party is anemic compared to Nintendo and Sony, maybe will change in the future, but today isn't there.
Third party content is probably better than other similar services, but seems to hit the service when the game doesn't sell enough and/or starts to drop in price. And for me one of the critical aspects of these kind of sub based services: they choose for you, so you have no idea if will really enjoy it. And games also come and go, so you can't also take the games for granted.
Reminds me of Netflix, i got it for free for 2 years, and it had relatively good quality content, but now quality is lower, price has been rised, and i have no promotions any more, and some shows i didn't have time to watch have are not there any more.