Everybody knows that Lee works the hardest. Just because others don't go to the extreme like Lee doesn't mean they don't work hard either. Everyone has to work hard to perfect a Jutsu, but those with special eyes (mainly Sharingan and rinnegan) can figure out and use a Jutsu like they were born with it, but they still need time to perfect it.
Everyone learns at different speeds, but that doesn't mean that they don't put any effort into their training. Lee has to work extra hard because he doesn't have any special skills. Naruto on the other hand only learns that fast because of his shadow clones, otherwise he would take just as long as normal shinobi. The only reason you guys say that Naruto doesn't work hard is because of his training methods, but why would he make things harder on himself if he has a way to do the training faster? Plus, he always has a time limit when he trains, so he need a fast method.