Impostor syndrome is not, in the United States, a recognized clinical diagnosis. By which I mean that Impostor Syndrome does not appear in the DSM, it does not have standard treatment, and no licensed mental health professional ought to offer it as a diagnosis to a client/patient. Clinical standards regarding mental health may be different in other countries, but given that Impostor Syndrome requires a high socio-economic status I would not be surprised if Impostor Syndrome were absent from other reputable standards of clinical practice.
Impostor syndrome isn't always a "syndrome". Some people really have lucked into positions which they don't deserve.
I agree that there are people who had luck. However in my experience those people are usually quite confident and don't have any problems with that. They know they cheat and are quite happy and relaxed about that, and have no wish to change it.