> Ik people tend to point to Russian, Chinese, and Indian Olympiad students as being examples of success, but most of them also attended top universities due to their Olympiad attendance, so I doubt the Olympiad itself had an impact compared to attending a Tsinghua, FyzTech (Citadel still hires from there for the London office at least circa 2023 despite the war in Ukraine and sanctions on Russia), or IIT Delhi.

Path to FyzTech lies through FMSHs which accept high school students largely via regional-level Olympiads. And path to that lies through the Olympiad "circle" in your local school.

You probably can build a stratified education system without Olympiads, but as a matter of fact in Russia they do actually play an important role in the overall structure.