You know, there might be a bit of truth in what you suggest (that DEI is rooted in PR), but does that really matter? Isn't a positive outcome still positive, even when the motive for the initiative may not be totally unself-serving? Canada's first bank, the Bank of Montreal, was among the first corporations to provide complete benefits to all of its employees and their spouses -- of whatever gender, colour, race or (I think) height. Most Canadian companies now do that -- even the little ones. The result is that many people going though life's ordinary difficulties are no longer burdens on the state (and thus the tax-payer) but are provided for by corporate (private) benefit plans.
What's more (and I can attest to this personally from having been directly involved), DEI and work principles are making companies re-think how they hire -- and that includes allowing hiring managers to see no personal information about candidates than the accomplishments on their resumes: not their names (which could indicate sex, race, country of origin), not marital information (which could hint at non-traditiional orientations). And they are abiding by them.
I grant, these efforts will never be perfect, because humans can't by their very nature be perfect. But I can't see any reason to let the inability to achieve perfection to stop us from at least trying to be better.
I'd push back a little on this, but let me try and explain why.
There are differences between the burgeoning DEI industry, and efforts to improve diversity, equity and inclusion.
If we looked at HR departments, we probably don't say 'Hey, HR departments are good, because we think humans are important'. If we did, I'd push back on that too.
Rather, good HR departments are good. And bad ones are horrible blockers to effective people management (in my experience). I'm lucky in that the current place I work has a HR department which sees themselves as a service within the business rather than gatekeepers. Of course there are some elements of gatekeeping (eg. Ensuring contracts comply with laws)
DEI is much the same. If they are integrated as part of the business, act as a service, raise awareness of diversity, challenge existing processes by pointing out issues and possible corrective actions, I can definitely see the point.
Instead I recently got to sit through the same pre-canned DEI slideshow and quiz as every other manager in my business, which is lazy, shows no connection to the business (which is a somewhat recent amalgamation of 7 businesses, and as such has vastly varied cultural norms around diversity), has no measurable outcomes, and would seem very unlikely to have much impact.
If I tried to talk to our clients in such a cookie cutter fashion I'd rightly cop grief for it. Any cursory measure of our business unit would show rapid increase in gender diversity across the group in the last 3 years, including at management level. My team also has increased diversity across racial and sexuality too. But the DEI team have never spoken to me about that, or even looked. Instead they send me a quiz to educate me on diversity and why it's important. It's frankly insulting.
None of that precludes the importance of diversity, equity and inclusion. But I wouldn't say the DEI industry is invariably a positive factor in that fight.