This will only be true when GAAS has spread to every conceivable player type. That obviously hasn't happened yet.
Look at Palia. There's a GAAS going for a completely untapped market which will do very little to harm other GAAS game populations.
Actually that's a good point. Most of the popular GaaS titles are in a limited variety of genre types. When we were finding out more about Sony's GaaS titles (well, before stuff like Factions 2 got cancelled), I was stressing that if they are going to push into that space they need to have a bigger variety of genre types in unsaturated parts of that market. Try and set a standard in a "blue ocean", so to speak.
A lot of stuff between Factions 2, Deviation's game, Concord, Fairgame$ etc. were seemingly FPS or military/shooter-based games, which is a heavily saturated genre in the GaaS market with a lot of strong competitors already. For example I didn't see a reason for Deviation's game being a military sci-fi FPS shooter, when Destiny 2 is already that type of game. Honestly, I'd
love if one of Sony's GaaS titles were a rhythm-based game; after all they set the standard for that genre with Parappa the Rapper, I absolutely wouldn't mind a live-service Parappa GaaS type game in that universe. It would be pretty cheap to make (can't see initial budget being above $25-$30 million), and relatively cheap to maintain with updates over a period of time of a few years like a Smash Bros.
Like I bet whoever makes a live service-based Wallpaper Simulator is probably going to make some bank.