I’ve noticed a pattern with movies that don’t tell you who the villain is beforehand e.g. in the trailers. They generally don’t turn out so well, and tend to be underwhelming.
Look at the latest Spider-Man’s trailer. So the villain is… a reptile? Why aren’t they telling you who he is? To be mysterious, or is he too boring to be in the trailer? Same with Captain America. Ok the enemy is some red faced guy wearing a human mask.
Compared to say, Spider-Man 2, which prominently features Doc Ock in the trailer, The Avengers, where you know they’re fighting Loki (and his army), and even Thor, where you at least get to see Loki.