It's hard to make a judgement here. I personally want to know everything and anything I can find out about my aquaria and how to be a proper caretaker. Knowing about the fish, the water, the plants and the bacteria, what they do, how they interact, the give and take going on, all can give me clues as to what my role is in the equation. Having said that, though, there are many who keep aquaria successfully with only the basic information.
In the end, I do believe the more I know, the better off my plants and fish will be. Whether it's required to be a successful hobbyist is another matter.