Yeah, Riku's deck was fixed. That is what made it more fun. My decks in Sora's story were structured so well, I almost didn't even have to look at them to know which ones did what, and they were all so powerful. As Riku instead of the deck being made by the player, the player had to adapt to the deck. You had to learn it if you wanted to survive. Yes, more difficult, but in my opinion it took more skill. Plus you didn't have to waste time searching for moogle points.