Capital accrued through the exploitation (yes, that's the legal and technical term) of labour.
There is 0 evidence that we wouldn't have a more productive society overall, if capital was more uniformly distributed across society; enabling more individuals to work for themselves or in co-ops.
Capitalist organisation structures are a pyramid with a very small few at the top collecting the vast majority of generated value. I don't think even the staunchest capitalism proponents can argue that a CEO no matter how good, is generating millions of times more value than a line worker at any org. Yet that's the kind of income deltas we see.
And we already know what happens when capitalist orgs reach a certain size. Rent seeking. They direct their resources towards preventing anyone else from competing in their niche through regulation and other barriers to entry. 'Why don't you go off and do your own thing?' Because it takes several million dollars to overcome the barrier to entry and even take a shot in any profitable industry. Exactly the kind of capital that average people don't have with the currently massively skewed wealth distribution curve.
If everyone suddenly had 5m in their bank accounts, you can bet your ass of millions of people would quit their jobs and go off to start their own things.
tl;dr: your employer isn't doing you any favours by hiring you and exploiting your labour. The fact that they happen to possess the capital necessary to profitably exploit you while you don't, doesn't turn them into a charity.