On its surface this card looks like it makes Robes of Endless Night entirely obsolete—a mere 1 XP for a 1 cost card that does essentially the same thing but for rituals too, and a wild icon to boot? So good!
But the pretty space robes aren't entirely done for. Crucially, the effect on RoEN is an optional trigger, whereas Ceremonial Robes is always the first spell or ritual of the round. So if the first spell you need to cast is 0 cost, the effect is wasted. Not to mention the upgraded RoEN that lets you avoid AoO. And you might prefer the 2 damage soak over a split 1/1.
In short, Ceremonial Robes are very good, I would absolutely take them, but there could be cases where you'd still prefer more expensive Robes of Endless Night.