1) If you have a criticism about them or their stupid name or how "'all I know is that I know nothing' how smug of them to say they're truly wise," rest assured they have been self flagellating over these criticisms 100x longer than you've been aware of their group. That doesn't mean they succeeded at addressing the criticisms, of course, but I can tell you that they are self aware. Especially about the stupid name.
2) They are actually well read. They are not sheltered and confused. They are out there doing weird shit together all the time. The kind of off-the-wall life experiences you find in this community will leave you wide eyed.
3) They are genuinely concerned with doing good. You might know about some of the weird, scary, or cringe rationalist groups. You probably haven't heard about the ones that are succeeding at doing cool stuff because people don't gossip about charitable successes.
In my experience, where they go astray is when they trick themselves into working beyond their means. The basic underlying idea behind most rationalist projects is something like "think about the way people suffer everyday. How can we think about these problems in a new way? How can we find an answer that actually leaves everyone happy?" A cynic (or a realist, depending on your perspective) might say that there are many problems that fundamentally will leave some group unhappy. The overconfident rationalist will challenge that cynical/realist perspective until they burn themselves out, and in many cases they will attract a whole group of people who burn out alongside them. To consider an extreme case, the Zizians squared this circle by deciding that the majority of human beings didn't have souls and so "leaving everyone happy" was as simple as ignoring the unsouled masses. In less extreme cases this presents itself as hopeless idealism, or a chain of logic that becomes so divorced from normal socialization that it appears to be opaque. "This thought experiment could hypothetically create 9 quintillion cubic units of Pain to exist, so I need to devote my entire existence towards preventing it, because even a 1% chance of that happening is horrible. If you aren't doing the same thing then you are now morally culpable for 9 quintillion cubic units of Pain. You are evil."
Most rationalists are weird but settle into a happy place far from those fringes where they have a diet of "plants and specifically animals without brains that cannot experience pain" and they make $300k annually and donate $200k of it to charitable causes. The super weird ones are annoying to talk to and nobody really likes them.