I see this, not to such an extent, in the Orthodox Jewish Community too.
Tay-Sachs is prevalent among certain communities that are descended from Eastern European (Ashkenazim) Jews.
Though the Orthodox are complex in certain ways.
The Satmar a very insular, but the Lubavitcher are very progressive in some ways.
I suppose both have problems with intermarriage, though to a much lesser degree.
After all, I don't think that you can convert into being a Mennonite or Amish, while Reformed and Conservative Jews can-theoretically-convert to Orthodoxy if they so desire.
Don't forget the most inbred bunch of goons in history: the royal families of Europe.