Gaston Bachelard introduced this concept. If I have a problem understanding limit and continuity, I should look around. Maybe my brain is defective, maybe my teacher made a mistake, and so on; but if almost everybody, everywhere is having a problem, maybe the limit and continuity concepts are special.
Given that the concepts were invented until the late eighteenth century, it is likely that humanity as a whole has problems understanding them.
I believe that Natural numbers, i.e. counting, is indeed natural, even crows can count. Some kids though can calculate square and cubic roots from a young age, Grisha Perelman, Ettore Majorana, Paul Erdos, Kenneth Wilson, and other great mathematicians; in some cases, this ability tends to interfere with others. Perelman rejected a million dollars, Majorana disappeared, Erdos abused amphetamines, Wilson has not lobbied the Nobel Committee to give a Nobel Prize in Physics to Donald H. Weingarten, for the numerical calculation of the nucleon mass.
Therefore I propose to take ALL children from the concrete stage of numbers, to the formal one of algebra, to end in the programming computational stage.
Let's all program modern computers.