How much did Nick Meyer or Harve Bennett know about Star Trek when they made The Wrath of Khan, The Search for Spock?
They may not have known a lot up front, but they did the proper research. Go read the old interviews and they'll talk about how they went back and watched the show--a lot. They just didn't egotistically move forward with their vision without knowing what came before. Sure, they changed things, but they were mindful of what they were changing.