If some person isn't willing to do company building because they are already at the cap so it won't make them any more money, that just means that someone else will do that. We have a planet of 8 billion humans; there's no shortage of human talent.
This is an untested assumption, as it takes quite a bit of CapEx without return to start a rocket company, or a tunnel boring company, or a car company.
From experience, there is a huge shortage of human talent.
Some people really are exceptional and there are very few of them.
How many Einsteins do you think are just kicking around? How many Robin Williams's or Tom Hanks's?
How many Kobes? We know not many because there's a huge search to find more.
There aren't 20 more Elons waiting in the wings there. Or 20 more Jensens. And so on.
It's actually far more rational as a society to pay the one guy who can create 100B his 10B for it.