STEM is hard since we can test for it. There are tons of bad teachers out there because they can be bad and we can't do much about it. But someone being bad at

STEM is hard since we can test for it. There are tons of bad teachers out there because they can be bad and we can't do much about it. But someone being bad at STEM is obvious and therefore all the bad people will get filtered out. That filtering is what people refer to when they say STEM is hard, the hard part is to not get filtered out, fields without such filters are not hard. Of course even fields without filters are hard to deliver a lot of value in, but that isn't what people mean. A person being a teacher doesn't tell you anything about how good they are at teaching, but a person being a mathematician or physicist tells you a great deal how good they are at mathematics or physics.