I suspect the way Microsoft does interviewing and performance management (very local to the specific team) contributes to the inconsistency.

MSFT has also been fairly open to its employees that it does not try to compete with competitors like Google, Meta, or even Amazon, in terms of compensation. So it isn't really trying to get the best engineers, so long as it can continue to print money.

There are still folks there who are incredible, but the floor is shockingly low at times. Folks will self-select, so you will then get teams which are more homogeneously good or bad.