The assumption is that more competent hires do a better job on average. Aerospace is not an easy field, but even in much more simple jobs competence matters.
Yes, more competent hires do a better job. But there is a limit to how much competence you can hire per person. That means there is a limit - or at least severe diminishing returns - to how much more competence money will buy you.
That means you can opt to spend that money on DEI without losing out on competence