I'm not really convinced that's the case. As I mentioned, the Russian system is apparently very much like this, and they don't seem to have a problem producing large numbers of advanced quantitative thinkers. I also take a little exception to the implication that I wasn't one of the "smart ones." I had no problem doing what I was taught, I got good grades at at an advanced prep school, and I scored just fine on standardized tests. I basically succeeded according to every standard set by the system, and yet I wouldn't say I really learned very much. To me that signifies a real problem. I certainly deserve some of the blame, but definitely not all of it.
You're not convinced of what exactly? That alternative methods reduce content? That is precisely what you are instructed to do by pedagogy researchers giving advice to teachers.
Asian education systems like India, China, Japan are very rigid and based on rote practice and memorization. "Prep school" there means evening schools where they just go do yet more memorization and rote practice to help pass entrance exams. Yet they produce many brilliant mathematicians too. Of course the students are motivated by parents and society, not love of cramming.
The ideal would be teaching that is individualized and does the best it can to get through to each student (there are plenty of efforts and even "edTech" that tries to do this, especially at lower grades). Without that it's always a trade-off in which students get the most value for the time spent.
You said it's "boring for the smart ones," which I took to mean that if we go by the methodology I'm suggesting, we'll bore all the smart students, they'll have less knowledge, and we'll produce fewer good ones. Maybe you didn't mean all of that, but if you did, my point was that the Russian system, which seems to operate this way, seems to do just fine in keeping good students motivated and producing lots of talented mathematicians. I'm not convinced volume of content = engagement and better outcomes, either for "the smart ones" or the rest.
