This is the central point of the article, and I don't think it's true. If it were as easy as "following a good process", then anyone could get rich investing.
There are also certainly other ways to have an edge in investing (quant firms come to mind), but I think the most realistic option for "anyone" is readily available in the form of low fee index funds and a long time horizon.
https://youtu.be/H5jPJQ5cVGU?si=KoXd4H3FOkLZ1y06 has an interesting counter-point. You need to fuel your returns with savings.
I guess it's a subtlety — in the end, since you said "for decades", and if you adjusted your wording sightly (such as "help you reach your financial goals", instead of "get rich"), the underlying message is similar. But I figured I'd share the link in case you find it interesting.
"Get rich" is definitely too broad of a target and probably has too many connotations with "mansion and luxury cars" when, as you identified, what I meant with that statement is closer to "financial goals" or, more tangibly, something like "comfortable retirement".