There are several additional things that level the playing field. Occasionally when there is a coach/QB combination you find a team which dominates for a few years but it’s the exception not the rule.
However it operates in a closed loop of the NFL + elite colleges so the draft system can work. The only bit that’s outside of that is this new international player pathway which Louis Rees Zammitt entered (and got an amazing contract with KC).
Football is not like that: players come from everywhere and there’s embedded corruption and entitlement as well as a ridiculous amount of global money for advertising/Tv/sponsorship. Assuming that the majority of money is in Europe*, to get a salary cap to work, it would require all the elite clubs of Europe to agree. That will never happen.
- obviously there’s money elsewhere, especially in Saudi