I appreciate your experience is different than the statistics, but it's quite literally less diverse than the US as a whole, and less than Minneapolis and many other midwestern cities.
[0]: https://www.census.gov/quickfacts/overlandparkcitykansas
Also, I likely see the younger people, there are quite a few old people who retire in OP. The blue valley school districts have a makeup that skews fewer whites (70%) versus a place like San Francisco where whites apparently send their children to private schools rather than public schools. So in terms of actually raising children to meet people who are different than them, it seems like the Midwest is a clear winner. Despite whites making up 40% of the population of San Francisco, only 20% of the enrolled students are white.
I don't think they meant that you can't own a house and lead a nice life if you're not straight and white. I think they just meant to say it's difficult to 'fit into' Midwestern culture if you don't fall into certain identity categories. While I'm from the Midwest and have fondness in my heart for it, I have to concede this is true from experience.
[0]: https://shawneemissionpost.com/2020/08/18/johnson-countys-re...