"It's incredibly hard to take a very diverse group of people and then expect them all to have compatible values, work nicely with each other and sing from the same hymn sheet"
Very true; BUT it's worth the effort.
BBC published an article a while back (here: https://www.bbc.co.uk/news/world-us-canada-49582852) pointing out the ways that the US (Western) Intelligence Establishment completely underestimated Bin Laden in the lat '90s, arguably leading directly to the 9/11 attacks. The premise is that a more diverse community working for the US government might have understood the message and prevented the attacks...
I work in a team that is incredibly diverse in background, nationality, skin colour, sexual preference, age etc, etc and yes it IS sometimes hard to agree on things; but generally people listening to each other and working from a basis of good-will tend to get to the right answer in the end.
Even if it takes us a bit longer to get to our answer than a cluster of 50yr-old white men might, I feel pretty sure that 9 times out of 10 we get to a better answer than any monocultural group would; and that is the benefit of having (and listening to) all those points of view.
**(Notwithstanding the above; I agree both that box-checking Diversity Surveys are a waste of perfectly good electrons and that any group of Old Etonians (or similar cadre of over-privileged representatives of the establishment education system of your choice) are probably a monoculture of thought no matter how apparently diverse they may appear!)