That old topic. Ironically, I find people who work with math (chosen to work with math, that is) to probably be quite unqualified to truly understand the problem. He opens by saying that learning avoiding mistakes before any bigger concepts is a major root of this but then again, people do make mistakes in math (even math professors) and it's a field where any mistake can completely invalidate the work. Also most people learn math for practical uses rather than as a science or field of research which also gives a different perspective (for most people, it's more important in life to not drop a zero when calculating a bill than it is to understand, say, a Homomorphism).

Math simply is hard. It goes against all our good-enough, subconscious brain functions we use every day to make basic "bigger or smaller" decisions. The problems mathematicians call "interesting" are counter-intuitive pretty much by definition and now imagine someone thinking like that writing a math book for children. The language used is vast and was built over literally millennia of mathematicians appending their own little modifiers above, below, and all around other mathematical symbols, resulting in monstrosities like the function for the Fourier Transformation which can actually be described quite intuitively geometrically.

Mathematicians want "simplicity" and "beauty" but their definition of either is absurdly different from any that would take into account basic human intuition. That's the problem. And there barely are any mathematicians that would admit that this could ever be a bad thing.