It's not clear to me that consolidation here actually does reduce diversity in a meaningful sense of the term. Many choices in the Linux world are not so often choices between truly different things, but between superficially different spins on the same thing.

For example, many distros only really differ from their parent in theming, replicated but differently named applications and so forth, which could all be offered in one distribution with less workload, but the same degree of genuine choice.

Same is true for DE's I think. Many of the things that differentiates DE's could probably be offered as configuration within one DE, with less workload but no or very little reduction in diversity.