My understanding is that the answer is more that there are more important/causal elements than X acting on Y. That is it.

For the college admissions example, the more important factor was what department you applied to. That had far more of a meaningful contribution to whether you were admitted than what your sex was. So, if folks wanted to increase admissions, you wouldn't focus on sex, you would focus on expanding departments.

That is the general trend with all of the examples. The paradox is you think focusing on X would be the important thing to focus on, but the data had hidden that there was a Z that you should instead focus on.