Look at it the other way — the article that you cited may serve to support the parent's argument, if this argument is that if diversity were actually a strength, then the companies that have embraced it would have outcompeted the backward companies that haven't; and we wouldn't be seeing discriminatory practices among the Fortune 500 companies, as the authors of the study that you cite claim to have observed.
You're assuming that companies outside of this set of Fortune 500 companies are less discriminatory. Maybe the Fortune 500 are the least bad.
Even if the Fortune 500 were the most discriminatory, their size and entrenched position in the market could allow them to stay on top in spite of this and many other weaknesses.
You are using "worthwhile" as "(morally) worthwhile (for (an appeased) society)".
The parent is clearly stating that, for a corporation, the main goal is to make money by out-competing its rivals. Society is not relevant, here. If such goal was reached by diversity hiring (no need to add "only" : if this policy added even 1% to the end goal, that would be a net positive), laws wouldn't be needed because, except for the most racist ones, companies would be fighting to get all those racially diverse people. Tech companies percentage of indians or chinese workers are very high without any coercion.
The simple reality is that talents can be found anywhere but that everybody doesn't have the same amount of talent.