Look at the level kakashi and itachi were at when they were 12 and 13 and compare it to naruto and his class. The strongest was neji and he was only low chunin level. Why do you think shinobi developed faster in the past?
This. Plus the fact that promotions were more easily given out. Even VoTE Sasuke could defeat that Kakashi.They were at times of war and were expected to develop faster