I would agree with that but IF SP was not around, more decks COULD be played. GDos and Trainer lock is played because of SP. If there were no need to counter the deck, other would flourish. I'm not saying the deck would not be played but it would not be a common as it is now.
Vilegar would be BETTER if it weren't for sp. No dialga and no quick bright looks/dragon rushes/drifblim fb snipes means that once a vileplume hits the field, the trainer lock is going to last the whole game. Gdos would also still be played because it loses to luxchomp. Also, without sp, it would become the fastest known deck, which is obviously a desirable quality.