First, very few people become millionaire CEOs. If thats your standard for success, then every path likely leads to failure because no path reliably leads to that kind of success. Some paths are more likely than others, but none are very likely for the average person.
Part of the reason for flat-ish career trajectory is that programmers earn more at the start than most. Some professions have more of a premium on seniority and experience than others. Senior doctors and lawyers for a combination of the above 2 reasons probably have steeper salary growth than programmers. That said, good 10+ yrs programmers do earn pretty damn well. 10 years as a doctor or lawyer and you're still considered a youngin.
Anyway, if you're the CEO, you aren't a programmer. If he's claiming that being a programmer is not a good starting point for becoming a CEO, I think he's wrong. Look at all the over 40s who were coders at some point, many transitioned into management or something else. Programming actually offers a lot more of that kind of opportunity than anything else.