Let's say you're trying to hire programmers. DEI could mean going to historically black colleges and women's colleges, and encouraging people there to apply for jobs at your company. This gets you more diverse applicants, from which you pick the best available, because your goal is to hire good programmers.

But what DEI actually means in practice is someone in HR keeping statistics on how many non-white-male programmers you have, and scolding you because you haven't hired enough non-white-males. That kind of DEI leads to non-optimal use of everyone's talent, because you hire non-optimal people for the job openings you have.