I have always said that the journey to chess mastery happens in two steps.
Step one is birth - 1400 Learn the "rules," and use them. Like develop, centralize, castle before you attack.
Second step is 1400- world champion. Unlearn everything you learned in step one.
What's the difference between 1500 and 2000?
What's the difference between 1800 and 2300?
Are the differences mostly degrees of the same things that seperate the 1300's from the 1800's?