Grandmasters spend enormous amounts of time doing opening preparation, in some cases creating strategies for and memorizing entire opening lines.

Is that going to help bad/beginner/average players? Not at all, in many ways they're not even playing the same game. Jumping to conclusions based on what Grandmasters do is therefore apt to mislead.

Granted, but saying worse players prefer closed positions is just false. Take the French defense, for example. Advance variation of the French is much harder for beginners compared to the exchange variation. And you can say the same for many other positions.