This is such a fundamental point. School should be teaching you processes of learning as well as knowledge. The problem is that the poor treatment of educators results in a reversion to the minimum. If you were taught 'acquiring as many facts/much knowledge as possible is learning' then you aren't going to see/understand this as you teach.
Teachers cannot really teach something they don't understand (general statement but...largely true). The reality is that most of what you think about learning and knowledge is embedded very very early. It is also, sadly, largely driven by social class in the US. The broad term is 'hidden curriculum' and much of the work started with Jean Anyon[0]. Much of the teacher workforce comes from working class and middle class schools. Below that, you don't go to college. Above that, you have economically more successful opportunities. Those are not schools that teach a fundamental approach to learning where the process or metacognition is part of the mindset imputed as part of basic learning.
[0] https://www1.udel.edu/educ/whitson/897s05/files/hiddencurric...