That may be your experience, but my experience is different. Before DEI was DEI in the early 90's, I was with a firm doing a ton of work for the government (RTC) and in order to earn the work we had to use minority subcontractors regardless of their qualifications. Most of the work they did, we had to redo. We eventually had to just use the minority firms in an administrative role as opposed to technical roles. We had very qualified minority employees; however, the minority firms were effectively just slapped together to take advantage of the government requirement.
May be apples and oranges to what your talking about, but DEI does have an impact, although the negative examples are often mislabeled as DEI.