This is where you will find your true 10x'ers. The developer who is so intelligent and experienced that they can accurately emulate an entire "level 1" user in their own brain for purposes of testing a UX/UI concept. Putting both a really clever design and a really stupid user into your head at the same time is very challenging. But, if you can figure out how to pull this off, you can rapidly arrive at designs that are intuitive for all without a bunch of painful iterations.
I've definitely seen the 10x that can't do this. Their UI design concepts usually turn out to look like something from a 4x game (and not a 'casual' one like CIV5). A user interface that exactly 1 person could enjoy using. About as clever as it gets and equally as worthless.
Try constraining the hell out of yourself next time you build something that a typical person would use (i.e. any B2C product). Ask things like "If I didn't know how to read, could I still find my way around this interface?". Clearly, this is too low a bar to effectively use some applications, but simply trying to aim in that direction over and over can help evaporate the more "clever" concepts in favor of your less skilled users.