Personal take on this, or why I don't feel quite as much like an imposter these days.
I've spent years toiling away in the salt mines of my choice convinced that I was just scraping by at every stage that didn't involve a formal "exam" (I'm good at those). Certain that I was surrounded by my betters. Because I'm in big science I got to do this in settings that involved a lot of close work and socializing with my peers; I've worked closely enough with scores of people at various points on their career arcs to get to know our relative strengths and weakness.
And I've slowly come to a realization which has taken (some of) the pressure off:
Yes, I suck and I'm really only good at a couple of the bits of this job and other people make me look like piker in almost everything involved in this work
... but ...
with only a couple of exceptions1 they suck too.
I really am better than average (even among my peers) at a couple of things. They are not big flashy things, they don't draw the admiration of crowds, but they are things that need doing and I'm pretty good at them.
So, I've become content (at least some) to be a worker bee: I've got a part to play in this enterprise, I know how to do it and people will ask me to do it because in these little corners they are even worse.
1 The only thing I can say about these folks is that they are few and far between and there aren't enough of them to keep me from getting work. And I try not to think about them. And I think I'll have another drink.
But it is inevitable for most of us. If you are N sigma above the norm, then there is one person who is N+2 sigma for every ten people like you. Unless you one of the ten smartest in the world there are going to be people who make you look like you can barely walk and chew gum at the same time. That is just the way it is.