this is just expectations.
you expect your skill to produce to you the thing you want.
and while your attitude is correct that you should step in try to research it, it wont necessarily live up to it.
even the greatest of all masters have more to learn. there is just to much for one live, to learn everything there is to know.
so the best thing, to me, is to lower the expectations. or to not set it like this-but rather treat your process-as it is-a process. not a target for finalized pieces. I mean , if you want finalized pieces, go for it, but don't expect them to be as you thought it would be. since as you said, there is a gap.
but, if you want to become professional, that might not be good enough for you.
what I've seen pro's do is make the illustration more simple, but deliver the same emotion. so you could concentrate on that minimalistic approach. i don't know what genre/style you are in, but everything can be simplified and even be better at transferring the emotions.
also, it might be that it takes alot more time, and that your foundations are solid enough. perspective to me is king. then its the rest, proportions/anatomy/gesture, shading/color, composition.
if your foundations are solid you should be able to tackle most things. perspective is killer. it takes a lot of training and proper one(not necessarily on this site, stuff like drawabox.com), to reach the level that you draw freely 3d depth like shapes.
hope that helps?