In theory, I'm a proponent of DEI. But your description is every description: "People have bias when hiring." That's the easy part to explain. A clear summary of how the solution can be fair is never quite spelled out (either because it isn't fair, or because explaining it clearly and briefly is intractable). "The fair amount of each of type person" is impossible to define, so there's no way to fairly get us there.

I.e. we can demonstrate that the scale is unfair, but we can't measure exactly how. The results of the bias are apparent, but the bias itself is unobservable. But when we put a thumb on it, that's highly observable, and we know the thumb doesn't know exactly whom to prefer over whom. You can't possibly expect humans to not revolt against that.

More practically speaking: Yes, the loud assholes focus on unqualified people theoretically being hired, but even if you dismiss them, there are still a bunch of people who won't be able to ignore the fact that, while DEI will cause the best candidate to sometimes be hired when they otherwise wouldn't, it intuitively causes the still-qualified-but-not-as-qualified candidate to be hired at least as often. Additionally, being denied by human bias (unconscious bias, charitably) is less angering than being denied by policy.