I know this feeling too well

Source:
https://reddit.com/r/...

If you've been reading about all sorts of stuff and not just doing the same exact thing that you already know how to do all these years then you do in fact have a lot of knowledge.

The leading cause of impostor syndrome is that it's impossible to enumerate a universe, that is, it's impossible to consider the set of all knowledge that you have about something, once your understanding is deep enough that you can integrate any new information just based on your field knowledge without fundamentally modifying your prior concepts.