I find this interesting to consciously think about. As an artist I think i subconsciously employ this conception of “cool” - especially since many of my character designs are weird creepy monsters that I want the audience to accept as sympathetic. A lot of hollywood character design is obsessed with giving non-human characters certain human details but the preponderance of those specific details has become boring itself and there are other ways to work the familiar into a strange design besides giving everything doll eyes.
I suppose it’s not a good metric for coolness as defined as an ineffable quality possessed by whoever your most cherished idols are, but that’s the wrong question about them anyway. You shouldn’t ask “what makes them cool?” you should instead ask “Why do I think they are cool?” - because other people may not see your faves as cool, may not even know who your faves ARE. Asking me why they are cool feels like asking me why your spouse is beautiful.
I’m not in the business of designing the next cool person who does a thing you consider cool, I’m in the business of designing cool art. Whether I end up doing something important through that art which makes me or my art cool in the “was important to someone” sense is not something I care to worry about. I don’t want to be important, I want to communicate what I care about - whether that’s important to others remains to be seen.