"Rationality is systematized winning" is a slogan that was adopted to patch a bug in human cognition. Namely our endless capacity to delude ourselves about how we did in an attempt to save face. The concept seems to have been absorbed, but I'm skeptical it's translated into more effective action. Certainly it produced many essays on why winning isn't happening. But the fact that we've been publishing essentially the same essay for a decade now implies something fairly fundamental is wrong. This slogan was chosen because it patches the bug, but I fear at the cost of neutering our ability to focus.
In one sense, "Rationality" is used to signify that something is part of the community that is associated with EA, Lesswrong, SSC, rationalist tumblr, secular solstice etc. If someone asked me "I have a successful life, what use is Rationality?" in this sense, I would probably reply there might not be any use at all. I happen to like rationalist tumblr and SSC and I like going to the SSC meetups at David Friedman's house, but you may or may not. Whatever floats your boat.
Now, if somebody ACTUALLY asked me "what use is rationality?" then I might say that I think education (not just schooling) is important because it helps us make better decisions, or I might say that scientific progress helps bring about new technologies that save lives and increase wealth. Or maybe, depending on context I may say something specific like "you're not going to solve your emotional issues with your ex by wishful thinking" or "if you don't understand your code how are supposed to debug it?" but only if I actually think they need to improve this region of their map in order to achieve their goals. If someone says, "No wait, what I really meant is, what use is instrumental rationality?" and actually means it, I would just facepalm because they're essentially asking why they should bother trying to get better at achieving their goals.
My point, is regarding what rationality actually is, I see no reason to exclude things that aren't part of Lesswrong et al. in trying to achieve my goals or in trying to learn. Should there be a community that is focused on giving people the cognitive skills to become more knowledgeable and more formidable? Yes, but we are not the only the only community focused on that, nor should we be. This is okay.