I think this depends on reference class and what one means by 'mistakes'. The richest financier is someone whose strategy is explicitly 'don't make mistakes.' (Really, it's "never lose money" plus the emotional willingness to do the right thing, even if it's boring instead of clever.)

Depends on the investment class. Even Charlie Munger (Warren Buffet's partner) says "If you took our top fifteen decisions out, we'd have a pretty average record."

I think the heart of the disagreement here is the separation between things that are 'known to someone' and 'known to no one'--the strategies one needs to discover what other people have already found are often different from the strategies one needs to discover what no one knows yet, and both of them are paths to success of varying usefulness for various tasks.

Yes, even if success in the domain is basically about avoiding mistakes, I imagine that if there are huge winners in the domain they got there by finding some new innovative way to get their rate of mistakes down.