Mmm how should i best put this...have you ever tried dancing? learning new dance moves? A lot of people learn by watching. I myself tried to copy MJ back in the day a lotl ol however some moves are simply hader to learn than others. Thats why video is so great because it gives you SLOW MOTION.
If you see something being done in slow motion it allows u to mimic/copy it easier. This is what sharingan does.
People if you dont believe me just go back and read the whole manga again and watch the whole anime again from the beginnin and pay VERY VERY VERY close attention to all the explanations they give about sharingan. Specially focused on Sasuke's sharingan since he's the one "learning" how to use it, Kakashi and Itachi were already skilled at it, so to truly understand how it works u need to focus on Sasuke.
In his fight with Haku, Haku's jutsu was supposed to be blindly fast moving at the speed of light or some shit, supposedly not even Kakashi would've been able to survive that under normal circumstances. But it was because sharingan allowed Sasuke to "slow" down Haku's movements (he didnt technically slow it down, his eyes just offered more insight into the movement).
COPYING JUTSUS IS NOT BY ANY MEANS A GIVEN ABILITY OF SHARINGAN. It's just one of the POSSIBLE uses for it. The user himself needs to be skillful at copying techniques. This is Kakashi's strong point.
And yes it is possible that he had learned a whole bunch of techniques by studying away, however ur all missing an important point. Most of the high level jutsus are forbidden jutsus or whatevr and u arent allowed to have access to them. And look at what we've seen from all the genin and that, aside from the basic crap they teach u at the academy, NONE of the genin have ever been seen to go someone in konoha to learn more techniques ther'es no LIBRARY of jutsus and shit.
They get theri superior techniques from their families or senseis. ALL OF THEM WITHOUT EXCEPTION. Which is kind of retarded for Konoha to keep a crap load of high level jutsus forbidden. But its apparent that they dont want just anyone knowing these jutsus, heck if i rememer correctly Kakashi said that only a few know how to do Kage Bunshin jutsu or is my memory failing me?