Sure there aren’t that many cards but those cards are so well balanced. Every single card has its uses so you’re constantly presented with interesting decisions. It feels like almost every other roguelike has dead time where you’re just going through the motions whereas in slay the spire you’re making decisions from floor 1.
I can’t help but respect spy mains because they play by far the weakest merc in the game. If your team has a somewhat competent pyro on spy duty they don’t get to do anything.