So what if he uses tailed beast chakra sure he's lucky to be born with a tailed beast in him but it's not like he didn't have to work hard to tame and utilize it's power to his advantage. Other characters rely on genetic gifts they received from their Otsutsuki heritage, the only characters who rely solely on pure human potential are Might Guy and Lee. Naruto's Bijuu chakra belongs to him just as much as Sasuke's dojutsu belongs to him, he's a Jinchuriki, that is his profession. Sure, take away his Jinchuriki powers and chakra he won't be as godlike, but still be an extremely elite ninja with superior chakra reserves, but same can be said if you take away Sasuke's eyes that he received from Itachi, or basically anyone's powers that they received through genetics. Yes some people are more gifted than others, naturally or circumstantially, all Naruto is doing is reflecting the real world because in the real world not everyone has an equal opportunity or equal physical potential. Rock Lee's point was to show how even though he wasn't physically or circumstantially gifted like the rest of them, including Naruto, he got pretty far through purely hard work, even if he couldn't get quite as far as his luckier peers.
Unless you're stuck on hollywood cheese, hard work alone isn't going to make you the greatest, there will always be someone who doesn't need to work as hard to achieve even better results, that's the unfortunate reality of life. But what does stand to learn from Naruto's primary method of developing his individual power, is that you can take something that was once a curse, like having a demon stuck inside you and everyone hating you for it, and make it a key to your success instead as long as you never give up and don't burn your bridges as friends and allies are necessary for success in this world.
