The kind you can find in most cities today. Where your neighbors come from many cultural backgrounds, but you don't even know their names, and they don't know yours.
Such societies are diverse statistically, but they are not integrated. In fact, it can reasonably be questioned whether they are "societies" at all.
> do you agree or disagree that your initial line of reasoning would support the conclusion that ethnostates are morally neutral?
"Ethnostates" are states dominated by a particular ethnic group. Which by definition includes states that are ethnically uniform. According to [1], many states existing today have essentially no ethnic diversity, including Japan, South Korea, Portugal, and Norway. Meanwhile, the most ethnically diverse countries include such luminaries as Liberia, Sierra Leone, and Ivory Coast.
In fact, if you look at the accompanying map[2], you will immediately notice a strong inverse correlation between diversity and living standard. Assuming the underlying analysis of diversity level is accurate, this map itself is a condemnation of the entire ideology surrounding diversity.
[1] https://en.wikipedia.org/wiki/List_of_countries_ranked_by_et...
[2] https://commons.wikimedia.org/wiki/File:List_of_countries_ra...