>>43529943Seasonal rules. It's like MtG or any other long running game that constantly gets new entries. If you allow everything you're constrained in what you can add, because something new, while balanced in a bubble, might have unintended interactions with a very old mechanic. Furthermore, if you want players to play the game legally (as in, not cheating or hacking) this means in order to be competitive, a player might need games and systems that haven't been available for 15 years. Alternatively, they can do the correct thing, which is seasonal rules. You can only use Pokemon caught or bred in the newest game. That way if a move like Power-Up Punch or Stealth Rock proves to be too strong and too widely distributed, they can nerf its availability without nerfing the move.
