Calculus is not only an important subject in math. It is also crucial to physics, chemistry, and engineering. Leetcoders earn so much does not mean these basic subjects are no longer important.
Lagrange, Euler, Gauss, and probably Riemann did not know what is "rigorous analysis proof of calculus". They still produced so many brilliant works. I don't think the issue is about rigor. The issue is that teaching calculus actually is not that easy, and high school teachers usually do not have the ability to teach calculus in a not-that-messy way. (To be honest, even many math PhDs can not teach calculus in a not-that-messy way.)