I know that the Sicilian Dragon is considered very risky for Black if White knows what they're doing; they can go for the Yugoslav Attack setup, play h4-h5 to break open the h-file, try and exchange the fianchettoed bishop, etc. in an attempt to checkmate Black. English setups with g3 seem to have a similar structure but with colors reversed, so why is e.g. the Catalan considered so solid for White?
I think the answer is threefold:
First white usually has a development advantage in the Catalan because he moves first, so any Black attack would not be so dangerous.
Second, white has a space advantage in the Catalan with his pawn on d4, while in the Dragon black's d-pawn is on d6.
Third, and probably very important, is the fact that it is not easy for black to exchange the fianchetto Bishop on g2 on the Catalan, because he generally plays ...e6, making it very hard or impossible to play Be6(f5, g4) Qd7 and Bh3. In the Dragon Be3, Qd2 and Bh6 is generaly much easier to achieve, compromising the castled position of the black King.
All positions in the Sicilian Dragon where Black managed to put a rock-solid central pawn on d5 are considered low-risk!
Domination of the center is critical for an attack on the side to succeed. The Dragon Sicilian would be considered solid if White didn't have the option to go for long castling and a pawn storm on the kingside. An analogous plan for Black in the Catalan would be suicidal.