It's not even so much about 90+ MC, but making industry-leading, genre-defining games. Something that should be expected of platform holders.
But Microsoft have sucked at doing that for the better part of 13 - 15 years. The only game they've made in that time span I can say met those requirements, and wasn't a pre-existing IP they just purchased, is Flight Simulator.
I would've put Forza Horizon in that category but that franchise has dimmed with FH5. Halo hasn't been a leader in the FPS space since Halo 3. Sea of Thieves is unique but it's not a massive success, nor is it at the top of kid-friendly GaaS titles (Roblox and Minecraft beat it easily, as does Fortnite). The new Forza looks worst than GT7 in many areas despite being current-gen only and releasing a year later. Gears 5 stagnated that franchise.
Compared to games like BoTW, ToTK, GOW 2018, TLOU2, Spiderman, Mario Odyssey etc., Microsoft hasn't cultivated much if any industry-leading or genre-defining games, and that isn't really going to change with buying ABK. It's a problem of bad leadership and upper-level management; they have no creatives or visionaries at those levels and it shows.