Parents, no. Mostly Gen X.

Their early-years and kindergarten teachers and teaching assistants are a bit more likely to be Millennials, and I suspect that is a factor.

If you assume that the slow drift in poor teaching started with Gen X teachers, then what Millennials would have lost first was some of the communication of the the joy of learning and metacognition, which matters when you are the first generation whose attention span is taking a battering.

It is perhaps harder to teach what you had fewer opportunities to learn.

They are like:

    Gen X   -> Millennial ->    Gen Z   ->  Gen Alpha
  1965-1980     1981-1996     1997-2012     2013-2024

it's really stupid, and people shouldn't use it (flag the article!).

Say "people born between YY and YY" or "people aged between YY and YY" instead.

Gen X

No, mostly Gen X. Gen Alpha's parents are more likely to be Millenials.