Explicitly in the American context DEI is primarily about hiring more members of minority groups at the expense of members of majority groups, based primarily on race and sexuality. This is perfectly exemplified in the FAA scandal.
In the context of DEI 'helping' the disadvantaged is never never done by expanding access to educational opportunities in order to find equally talented people who have been financially excluded or barred entry by prejudice. It is always a matter of lowering the bar for certain protected groups, and often also a matter of removing opportunities altogether for members of perceived privileged groups.
This is especially visible in the arts and education here in Europe - where funding and employment opportunities are overwhelmingly based in exclusion. Primarily of straight, white, cisgender men. You site the example of young white men in the UK having worse outcomes. Please point me to a DEI initiative that targets employing them over other groups. What happened at the FAA is what always happens under the banner of DEI, capital A 'Antiracism' and other successor ideology initiatives. The goal is never fairness, and always power.
The issue with these approaches is simple. They are massively divisive. Rather than aiming to address prejudice, hiring bias or systemic barriers to entry - they actively create them, with the justification of historic prejudice. I heard a joke once in college - whats the difference between an activist and a social justice warrior? An activist sees a step and builds ramp, a social justice warrior tears down the stairs.
DEI is a bad idea, rooted in bad ideology and the stolen valour of movements towards genuine equality. As is any ideology that privileges members of one group over another - however 'noble' its adherents pretend to be.
If you're advocating for approaches like blind hiring, or addressing poverty, or providing educational aids to help neurodiverse or disabled people, or free school meals, or free university, or increased arts and community funding or any of a thousand other initiatives that help people based on real need rather than perceived privilege, you'll find me and many others whom you presume to disagree with support you. But the entire brand and practice of DEI and associated initiatives and terminology is beyond saving.