Thats becuase since pokemon is a kids game,or made for little kids, they had to lower the difficulty so they could play through the game. I also noticed the difference when i replayed x and y with heartgold and soulsilver. Really big diff. I actually had to be careful of which pkmn i took with me, while in the newer games, i didnt even have to switch that much, and not even in my party too. But at least their story plot is gerting better :/