To be fair though new content like missions and a major updates will really take some time.
Consistently every time they release a new set it has been with a story, new skills, cards, opponent decks and stuff. It take time to make those especially new skills which still have to be tested on impact to the game. Also they have to space major updates properly so as not to burn out new content fast. New ideas that are good don’t just come up easily.
Though i would like to have new content i wouldn’t like a crappy story and skills that just throw the game out of whack.