by definition, a group who are better at rationality win more often

Well, there is this "valley of bad rationality" where being more rational about part of the problem but not yet more rational about other part can make people less winning.

Sometimes I feel are we are there at a society level. We have smart individuals, we have science, we fly to the moon, etc. However, superstition and blind hate can be an efficient tool for coordinating a group to fight against another group. We don't use this tool much (because it doesn't fit well with rationality and science), but we don't have an equally strong replacement. Also, only a few people in our civilization do the rationality and science. So even if there is a rationality-based defense, most of our society is too stupid to use it efficiently. On the scale from "barbarians" to "bayesians", most of our society is somewhere in the middle: not barbaric enough, but still far from rational.