The question is, are more of them rich from salary, from capital ownership, or from inherited wealth?
In the US, the broad “rich”—about the top 1% by income—overwhelmingly make their income from salaries and wages (https://www.cnbc.com/2015/04/09/where-the-rich-make-their-in...). However, the ultrarich—say, the top 0.1%—tend to make it from capital and inheritance.
Assuming financial gurus are trying to give feasible advice for how to become comfortably rich, the safest bet with the highest expected value is probably something like “get an elite professional education and find a spot in the elite managerial/professional class.” I.e., banker, MBA, corporate lawyer, or (for all the HN readers) FAANG engineer.
The underlying gist of “You’ll NEVER get rich by working for someone else” is that you should look for opportunities to build wealth that’s not tied to hour-by-hour labor. You can do this by owning your own business, or by looking for ways to own equity in valuable assets beyond your regular job.
I mean, enterprise software sales folks can get rich being paid on commission, "influencers" can get rich being paid by affiliate links, and none of them have any ownership in the business.