I agree in principal, but: The people at the frontier aren't alone at the top of a mountain, they still have each other for guidance. The master that transcended limits while in isolation is a literary trope.
But the OP was making a much stronger claim, that it is, in principle, impossible to learn anything on one's own, and that HAS to be wrong, for the reasons I listed.
When I sat with 30 other testers for 6 days per week I achieved mastery I did not believe possible. Eventually I could cakewalk even the most difficult challenges in those games and I was generally recognized as a highly talented tester.
Meanwhile I’ve sunk more cumulative hours alone into Elden Ring and I have accepted I will never reach that same level of mastery.
It’s a humbling realization how much of my prior greatness was actually just my environment at the time.