You forgot quantity there. I subscribed for 2 months and finished Wasteland 3, Battletoads, Grounded, Ori and played enough of Flightsim to know that it's not my cup of tea. Now I'm in lockdown, bored out of my mind and staring at 200 games thinking "nope, nope, nope". It's only $10 bucks but I cancelled anyway - because people are cheap bastards like that - waiting for new big releases before I sign up again. For MS to prevent this they'll need 3 things
quantity so every month there are a couple of A or AA games that'll make people wonder "what's next?!"
GAAS games that people can play forever
Or just cut normal AAA games into episodic content
Adding stuff to spider man is not the same thing as what they're doing with Halo. Games like Spider Man maybe get some DLC and then we're waiting for a sequel. With Halo there will be no sequel, they went full destiny on us. Not saying that is bad, we still have to wait and see how that'll turn out. All I'm saying is that they didn't make Halo GAAS because of design choice, they made it like that because of a business decision. And they'll probably do the same thing with most of their IPs.
If they end up offering just those three things, will you keep your subscription?
Well, yes, probably. All depends if I keep enjoying those type of games. I love Halo but I have no idea if I'll enjoy a GAAS version of Halo too. If its like Destiny then it probably won't be my thing.
That's why I would have loved to see how MS will be handling Halo Infinite before they start snatching up whole publishers with the sole purpose of growing GP subscribers.