Math skills are probably malleable to a certain degree, nobody is disagreeing with that. Someone who got a C in algebra can probably get an A with a better tutor and some motivation. But as engineer(-ing majors)s, we shouldn’t make vague qualitative judgments like this - this just begs the question of how much we can reasonably improve. I cannot win an IMO gold medal nor can I ace the Putnam, and an average student probably cannot get a P.hD in mathematics. This view is not mutually exclusive from believing that math skills can be improved to some extent and that we should encourage kids to try their best.
And with all due respect, I don’t know why you’re claiming that I think math aptitude is “innate” when I have explicitly stated that I do not think that this is the case, and gave an anecdote of my own abilities improving.