I don't think anyone disputes that high-level sport can make you more vulnerable to particular msk issues than people who have led a less physically extreme existence. Overuse is a real thing! The relationship between cumulative load and tissue health is more complicated than you acknowledge, however. High cumulative load over life can be protective. Professional marathoners frequently have better knee health than sedentary people, yes, but also age-matched recreational runners, which is not what you'd expect if extreme load was straightforwardly harmful in the way you seem to think it is.

Regarding your comment on cortisol. Plausibly the relationship between cortisol and behaviour here is bi-directional, as is common with hormones. High testosterone influences me to go to the gym and my workout influences my testosterone, etc.