Hot take, but I don't think it should be such a taboo if individual institutions have "insular culture". As long as there is heterogeneity amongst relevant institutions, the synthesized literature can still be very productive even if e.g. MIT has a bias towards a particular way of thinking.

Conversely, I think it's problematic for scientific creativity how homogeneous behavior across institutions has become. I don't believe it is a result of this cross pollination requirement, but rather causality probably goes the other way. Many old professors at MIT were true lifers, from undergrad to PhD to faculty. Postdocs were often skipped entirely, or looked more like a 1 year visiting researcher gig.

Regardless I don't feel there should be a viscerally negative reaction to individual institutions having clear characteristics. It's true that objective evaluation is hard, but it's hard anyway honestly.