Am also an introvert, and it does reduce the possibilities, in my opinion. Still struggling with that. But trying to meet technical people who can hire or refer you is pretty useful (and try to maintain relationships like that when you leave a job).

Location is a problem. If you move to a place like BA or NY, you can probably double your salary right off, even if your skill level is rather low. This is very hard, though, if you have a family or your local social connections are important.

I doubt you're an imposter. Most of the people I met at my high-paying jobs were no more skilled than those I meet in the hinterlands. (And the brilliant ones are often insufferable.)

Rich companies are rich, so they can pay more. That's about it. There's a lot more competition for high-paying spots, but generally the people hiring are doing it pretty randomly. Having a resume that looks good and being able to talk a good game are more important than actual skill.