This is not true. We have two guys playing in our KD who I would consider amongst our top core players (and would probably do well banking if they wanted to) that have played about 2-5 ages each before joining us. Because there's less new players, naturally there's going to be less good players. The cream will rise to the top, but with less new players there's going to be less really good players to challenge the established top. That doesn't mean that good players that get the game almost right from the start when being taught by ghetto monarchs, can't rise to an acceptable level of play where they can challenge the top.
Should be way less than 25% against a good cow player. Any cow that has only 2.5 raw and 4 modded wpa/tpa near the end of the age, having been at his max size for a while, is an absolute nub and shouldn't deserve to play a cow.