Some people might get caught in a Fi-Ni or Fi-Si loop and seem less...relevant or easy to relate to.. (or something), but I think both Ne and Se helps round many Fi types out, if they really use them. And you can't use them without being in the world somewhat, and observing things. You can't be Se or even Ne without looking outside yourself. Some of us introverts might be too introverted for our own good at times, and just sit on a chair indoors with our ideals/values/Fi, but if they did that for too long, they might as well not even call themselves Ne or Se. Because they're observation is barely existent (or rather, applied indirectly), where Ne or Se is playing almost a third role, instead of secondary. At a certain point, people need data, and over time, that fleshes things out, and Fi isn't just coming out of nowhere, but out of experience, and observations on what works (as they see them).