You don't require that they all actually gain power, wealth and prestige (since that measures something else, which could be equally important or not, depending on your perspective).
If the only way to become a SCOTUS justice is to get into one of 2 or 3 law schools, and only people with a narrowly defined profile ever get into such schools, you pretty clearly do not have equality of opportunity. You can establish this even though in reality almost nobody ever becomes a SCOTUS justice.
If they're measuring the diversity and inclusion of the pipeline, they'll still end up failing. Warsaw (one of the most diverse Polish cities) doesn't have a significant black population. They might get a handful of Chinese or Vietnamese applicants. The bulk of the "foreign" population are Ukrainian (by a wide margin) followed by European.
The trouble with any metric used to prove DEI credentials is that the org starts changing behaviour to boost that metric.
Perhaps the metric should be aligned with availability. No idea how that would work in practice though.
Equal outcomes for everybody.
This is how you get 100lb women in the fire department who can't even control a fire hose at full pressure.