I dont have issue with mathematics, but understanding math is always requiring lot of time and effort to understand, and most people dont have this sort of time or mental energy available, or they dont value mathematics problem solving enough to invest too much time into understanding it, or have other things to solve that they think is more important.

Understanding new mathematics concept or formulas always takes time and effort, there is no black & white barrier where someone understand all the mathematics at once, its all about time spent into understanding some bits of it, and the more time you spent reading it the more you understand.