Re-read my post, I clearly said that "that doesn't mean that Naruto, Sasuke, etc do not also work extremely hard". My point was that when one chooses to use curse seals for power, it invalidates much of that work, because the seal is no substitute for real power, of the likes of Itachi/Oro/Jiraiya kind of level. If anything, having the seal seems to cripple characters progress.