the stuff they come up with by thinking for themselves is usually not all that great by my standards

They are just humans, aren't they? I am afraid that at this moment it is impossible to assemble a large group of people who would all think on LW-level. Not including obvious bullshit, or at least not making it a core of group beliefs, is already a pretty decent result for a large group of humans.

Perhaps one day CFAR will make a curricullum that can replicate rationality quickly (at least on suitable individuals) and then we can try to expand rationality to mass level. Until then, having a group without obviously insane people in power is probably the best you can get.

I am worried that I am giving UU too much credit because they happen to use the word "reason,"

You already reflected on this, so just: don't emotionally expect what is not realistic. They are never going to use reason as you define it. But the good news is that they will not punish you for using reason. Which is the best you can expect from a religious group.