1) If you add a large number of people then mean averages will drop off. This is simply a mathematical truth.
2) People who weren't here during the earlier days of the game when there was less content in general are likely to be less familiar with the workings and limitations of the foundry--this is equally true of both f2p players and new subscribes.
3) The nature of the dilithium grind is also playing a substantial role here. I have noticed in the chat box, more than once, people saying they rate anything under 2 minutes a five and anything longer a 1.
4) Mean-spirited elitism about the innate inferiority of the f2p players is poisoning this game.