I might be alone here, but I never had the impression, that AD carry was "simple". Not even when I was new to the game. AP carries always seemed much simpler to me - get into position, use your spells and then survive, while surviving is easier, the better you positioned yourself and the better you used your spells to kill or lock down opponents.
The only "AD carry" I'd ever play was Kayle, because I had incredible utility, burst and was more or less a caster as well. Especially the optimal use of the ultimate is easy for me. Sometimes I even played Ashe, but besides throwing good ultimates I was really bad with her.. I don't know - I realize what an AD carry "should" and "has" to do, however I could never get into that mindset of actually executing it.