I'm always on about how what the rationalist community is missing is the robust social norms of eg anarchism.

But another aspect is anarchism gives a sense of identity, commonality, and place, that's more historically sweeping. The rationalists are very big into feeling like they're inventing everything important on the spot from scratch. Whereas anarchism has two centuries of experience and experiment to pull from, and a wider sense of continuity with millennia of liberation struggles.