There's no piece in the entire repertoire that can't be learnt with slow, regular practise. End of story.
An interesting Dissertation is [Rediscovering Frederic Chopin's "Trois Nouvelles Etudes"] - Qiao-Shuang Xian. The monograph’s five chapters deal with specific aspects of these works.
But, my question is, what is a long time? I would like to think I'm alright for how long of I've been playing, but I don't know if that's really the case. How long does it take most people to play their first etude, and what etude does that tend to be? And when people say this many years, that's assuming I practice how much?
One measure at a time is right! that's how I am working on 10-4. I'll just bust if it ever gets up to speed!
I have played them all...A good thing to do is to begin by choosing a less-difficult one and isolating the particular technical part of it. For instance, take 10/9 - so just practice the first four measures, left hand alone, for a few weeks before you actually begin learning it. In other words, isolate the difficulty and turn it into a mini-exersize for a while. Then you will be prepared for the work ahead, you will be familiar with the particular demand, and you won't be so overwhelmed.
did you do this on all of them?