First of all if you solve problems that means you know enough of the subject to reason out the solution, it may not be perfect but very few solutions are.

I have been working on legacy code and maintaining old c++ code for a decade (200.000 loc) and most of the time I had to spend days debugging and reading code just to understand enough to get a possible solution, and then I still end up writing a solution that breaks in a different corner case that I never could have imagined.

So yes most of the time you feel like you don't know anything, but over time you end up knowing a lot of how that codebase works. And after two years you must have picked up something about what you are working on.

Then you have those programming language genius colleagues, that know all the tips and tricks of a language, I use them to get ideas on solutions, because they always have an opinion on what is the "right" way of doing stuff.

That's just my 2 cents.