Many a healthy above median earner is unaware of the privileged shortcut to capital class available to them. Spend a third of your income for nine years and you're there. Make that a quarter to finish in six years. Especially for dual income people without dependents, that's quite feasible.
Not diminish your analysis. I just hope it adds a bit of perspective.
There is no “shortcut” to vast wealth, because if there were then everybody would be using it as the default and it would no longer be a shortcut. What are often described as “shortcuts” are highly situational opportunities with lower-than-typical risk, which by virtue of announcing them to others means the opportunity has passed and the risk has increased.
For there to be vast amounts of wealth hoarded by a few, there must also be vast amounts of exploited people desperately getting by on table scraps. There is a finite supply of wealth, and if we do not build systems to redistribute it equitably then it will always and inevitably by hoarded by the few lacking a moral compass or basic empathy for their fellow man.