I'm in agreement. I have 4 college degrees that are only glancingly related to what I actually do for a living. I got my first job in this by embellishing my credentials and showing a knack for picking up new skills quickly. That was 17ish years ago and I have quite a nice career doing a thing I didn't know existed when I was in grad school. This is, honestly, the sort of successes being a gifted adult gets you in real life.

That made me feel like I had to put some effort, but I only did so for my own assignments; when it came to listening to other people's presentations I felt like I "didn't understand anything"; overcomplicated thoughts running through my head; also think that I was feeling quite bored by the subject at times.

Do some reading about "imposter syndrome". When I discovered this was a thing it really changed my whole concept of myself. I now work in a company that has tried carefully to cultivate an environment where people feel say to admit what they don't know, and it's amazing how even the cleverest people I work with, who do great work and ask snappy questions in meetings and so on, really don't actually know more than me.