It’s good of you to take the time to compile your observations for the benefit of younger numberphiles. What you have described rings true from personal experiences and observations of professional mathematicians.

I would agree that the content and pace of delivery of most of primary and secondary school maths education is not well suited to young gifted mathematicians but that is because the curriculum is designed to fit as many as possible and therefore targeted at some notion of an average student. I have widely expressed praise for the digital resources which allow young numberphiles to quickly yet rigorously cover all the foundational materials.

Calculus, in particular, seems to be frequently debated with respect to whether it ought or not to be included in the high school syllabus, with many secondary school educators advocating that it be replaced by maths topics with greater apparent day to day relevance, but fortunately it remains in the secondary curriculum as it is an integral part of the foundation for applied mathematics and physics, for those who later decide to take up further studies in these fields. My son was fortunate enough to have been in a radically accelerated stream for maths so he finished high school extension maths in year 11 - the calculus and vector maths he learnt stood him in very good stead for his in depth physics investigations this year, which I hope will give him a strong start for his planned R & D engineering studies and possible career in the renewable energy sector.

Everything in our physical reality obeys universal laws and rules which requires an understanding of their mathematical bases to understand and work with - whether or not the majority appreciate this truth, it’s great the maths foundations are laid at each stage of education, to enable those who are interested in understanding physical reality, to go on to further studies.