Imposter syndrome is, ironically, most often felt by real imposters; I won't deny its existence, but have never seen even one example of it. In every instance, I see the phrase used by the incompetent as a shield against reality and against their observations. People who very obviously can't do tell themselves that they can and, despite repeatedly failing, keep insisting it's but an internal state.
Imposter syndrome is, ironically, most often used as an excuse to avoid improving oneself, to forego the necessary steps to transition from incompetent to competent, from imposter to poster. A genuine lack of enthusiasm seeps from every hole of the imposter's life, and is deeply related to fixing it.
Imposter syndrome is, easily, corrected. I've never been afflicted so, because I accepted ignorance and sought to correct that rather than bemoaning being ignorant. One could argue ignorance be ever-present, but it certainly becomes less of an issue after enough education. Everything I create is a monument to my competence. I needn't fear introspection or looking upon my works, because I decided to build things and pursue a life of which an imposter wouldn't be capable; while opinionated, every problem needn't have a clean solution. It's a matter of confidence, alongside actions to defend it.
This solution isn't common, from what I've seen, because most imposters are unenthusiastic, and it's much easier to cry for pity from strangers. There's innate ability, without which one never will be able to be anything but imposter, but the matter of proving its absence lies in how this is treated.