Forcing users to use certain identity providers while uninformed as a sole point of failure is a challenge.
Apple (or other providers) already have the user with an ID, having the app do the bidding of propagating it's use further is a different issue.
If it was optional, and a convenience/preference that could be added, that would be a different thing.
M365 login specifically can hook into quite a bit of organization information along with the user itself that can help configure apps, wouldn't be relevant for Apple in those kinds of B2B scenarios.
Apple ID is almost always a personal or individual one.
It can be convenient for sure, makes me think about how there's other things where Apple is/was the only choice for the most part like payments, although that's changed for the time being.
Most people are where they started, whether its Microsoft, Gmail, Apple, etc.