There are people who are impostors who don't get impostor syndrome, impostors who do get impostor syndrome, non-impostors who get impostor syndrome, and non-impostors who don't get impostor syndrome.
The first category is often full of narcissists, who think they know more despite evidence, or literal cons like described in the post.
The second category is people who are unfortunately correct about their situation, but perhaps they should be happy they've got the job they've got. If they detached their sense of worth from their work they might be a lot happier.
The third category is people who think they're in category 2 but are more competent than they know. They underestimate their own abilities, either because of a belief that their skills are misplaced and they won't transfer to what they're doing now, or they have some unresolved anxiety issue, or something traumatic happened in their past, or they're out of place in terms of culture and fit, or a dozen other reasons.
The final category is where we all want to be. Sometimes people in category 1, in service of helping category 3 and hurting category 1, try to make it seem like they actually don't know what they're doing. I don't think this is healthy though. If you know something, you should be proud of knowing it. Furthermore, if you have power, you should recognize it, if only because you should know before you hurt someone else.
IMHO this is why we've ended up in a society where no one takes responsibility for their own lives. Everyone wants someone else to take responsibility - usually either a company or a politician. Everyone wants to stop climate change but no one will stop eating meat or flying on planes. Everyone wants a more equitable situation but most people donate hardly any part of their salary at all, even if they could. People want privacy, and to use social media services for free, with an unending list of features. I could go on and on about what people will do to shift the blame onto someone else.
I don't want to say there's no such thing as structural issues, there are economic issues and political issues which legitimately need solutions that are global/social/political. Just because someone flies somewhere once a year doesn't mean that they should die from heat stroke. It also doesn't mean that a company should be allowed to pollute 1000x that single flight every minute of every single day. It's just that these are the logical consequences of a society where no one takes responsibility.
Deciding to not take responsibility because you think that you are not capable of being responsible sounds responsible/good/morally correct - but it isn't if you actually are capable of being responsible. And I guess that's my gripe with impostor syndrome, it feels a little like a dodge or like an excuse. I'm never sure how to evaluate that excuse, and compare it to other excuses, and which excuses are real and which ones are fake. I'd like to live in a culture where people with impostor syndrome were helped, but the condition wasn't glorified, so I could always presume the excuse was real. Maybe our culture should just be more clinical about these sorts of things.
The final question then would be, how to create a culture that is more clinical, or more objective about certain conditions. How do you talk about performance in an objective way? How do you talk about (mental) health in an objective way? We're really far off from being able to do that, but at least it puts everything into context. It also gives a fairly simple actionable plan to those with impostor syndrome - how can you objectively measure your results? How about other peoples results in a similar position? What metrics would even make up an objective evaluation? This is where you have to be very careful, after all, if you are in category 3 you are likely to design metrics that punish you at the benefit of others. You don't know as much about other people's mistakes as you do your own. You have to be very very careful not to do this. After doing this, you will know for sure if you are an impostor or not. Once you know, either way you won't be bothered by it anymore. You move into category 2 or category 4, and you can learn to accept what you are from there on.
Just don't sit in this in-between of pretending to be confident to other people but not actually being confident. That will eat you up inside. That will eat up the whole world, if we're not careful about it.