This cogently argued point highlights a necessary issue in self-help, namely the lack of diversity.
However, there is another issue that underlies and actually predicts this lack of diversity - and that is that self-help, by its name and intent, relies on the self to help.
If you are dealing with societal issues, telling the "self" to "help themselves" out of it is like looking at someone drowning in quicksand and urging them to hurry up and push their way out of it.
When there are societal, structural barriers to wellness, whether for some type of widely-recognized minority group, or for groups that have no recognition-at-law (ie: the HSP or highly sensitive person), there is no solution in self-help.
The problem is not the "self". It's the societal structure that provides only certain "ladders" out of specific "abysses", and leaves everyone else to wander without the same structure, while, yes, exhorting them that if only they work hard enough, they can do it. Themselves.
Only those for whom societal structure is invisible or inconvenient will be able to ignore the stats and insist that anyone can do it, despite the fact that groups who do achieve it are not evenly distributed across the spectrum of humanity.
This is a large part of why I am an anti-self-help writer.