Approximately no one in the community thinks this. If you can go two days in a rationalist space without hearing about "Chesterton's Fence", I'll be impressed. No one thinks they're 100% rational nor that this is a reasonable aspiration. Traditions are generally regarded as sufficiently important that a not small amount of effort has gone into trying to build new ones. Not only is the case that no one thinks that anyone including themselves is 100% correct, but the community norm is to express credence in probabilities and convert those probabilities into bets when possible. People in the rationalist community constantly, loudly, and proudly disagree with each other, to the point that this can make it difficult to coordinate on anything. And everyone is obsessed with studying and learning, and constantly trying to come up with ways to do this more effectively.

Like, I'm sure there are people who approximately match the description you're giving here. But I've spent a lot of time around flesh-and-blood rationalists and EAs, and they violently diverge from the account you give here.