I think their self-criticism is an act, a sham to make their arguments look stronger. They pick battles they can win and don't engage with ideas that really are challenging to their reasoning methods or priors, especially if they come from outside the rationalist community.

It's like this:

I can write an unbreakable cryptographic system by inventing one, going through the motions of making up attacks and showing that those attacks are impossible, and then concluding my system is unbreakable. Anyone can design cryptography they themselves cannot break.

Ask any cryptographer how well that works.

This is pretty normal human behavior, but it's not rational.

Yeah but would they ever admit they were wrong about things they published themselves? Are they open to criticism they didn't come up with themselves?

I feel (but gut feeling, I'm just an internet commenter / shitposter that doesn't have the time or inclination to fully engage with these people) that the bigger rationalist bloggers all stand on a tall soapbox, broadcast something, then disappear into their own head again.

Ahh yes, the extreme intellectual humility of lesswrong and the EA guys! ;)