The "path of hard work" is inarguably a central theme in the manga. Consider the conclusion of the Naruto/Neiji fight -- "Bunshin was my worst technique." Ultimately, the hard work ideal falls into the nindo ideal that different characters pursue. What you need to understand is that it's not the specific ideal that they follow that's important, it's the strength of conviction that's important. It's a central theme that allows the author to illustrate actual accomplishment.

For example, it was quite necessary for Rock Lee to be beaten so badly by Gaara. Not because of power levels or a lack of effort, but for the writing. Lee gains his power by overcoming adversity -- without an impossible challenge, a handicap that makes him unable to accomplish his goals, he's not Rock Lee; he'd just be another paper-thin character that we don't give a damn about. Originally, it was lack of talent that held him back. He just couldn't compete without proper jutsus. Through his sheer force of will, he put forth the necessary effort to do the impossible -- to be a top-class ninja with only Taijutsu. Not only was Gaara necessary to further the plot, but Rock Lee would have "capped out" if he had won that fight. His hard work wouldn't take him any further because he had accomplished his goals.

However.

However, through his incapacitation, Rock Lee's got a new lease on life. He's got another mountain to climb, and he will once again do the impossible. Lee will not only recover from his handicap -- he will become stronger than he had ever been before.

And it's all just because he believed.