I think the thing is, at any given time, there may be a thousand people trying to do the same thing at a certain level of competency, with only a few actually managing to gain any traction due to a combination of luck or timing.
Then these people say they were much better than the others, while objectively they were executing at about the same level.
If everyone does everything right, there will still be winners and losers.
The mythology is that hard work + cleverness = success.
The reality is that probability * (work + cleverness) = success.
The size of the probability makes a big difference. If it's too low you're likely wasting your time.
You can improve it with good business/sales techniques, but if it's tilted the wrong way you're always going to be fighting against it.
Objectively, you'd need to know the hit rate for specific business ideas/approaches/fields.
Realistically, some fields are more likely to be successful than others. Analytics, sales aids, and off-shore arbitrage are far more likely to make money than - say - software support for the disabled, or starting a band.
Then these people say they were much better than the others, while objectively they were executing at about the same level.
If everyone does everything right, there will still be winners and losers.