The big economic growth success stories of the last 50 years were in China and East Asia: Japan, South Korea, Taiwan, Singapore, Vietnam. Some of the least diverse places on earth. Many of these wont accept immigrants from other backgrounds at all, although they might accept low wage agricultural workers.

Economic growth in the US over the same period was mediocre, with declining productivity, and in Europe, it was anemic.

There is just no evidence that nations which focus on diversity in and of themselves have had better economic outcomes.

Now it does make sense that if you are in a large multi-ethnic society then you will be at a disadvantage if you only hire from one group, since good people are hard to find, so why limit yourself to just a small subset of the population. This is less important for a small company than a large company that really needs to cast a wide net. So not intentionally excluding subgroups of your population makes economic sense.

But I'm not aware of any evidence that being more diverse than your population will improve outcomes.