I like big fat fantasy books. I don't like reading a big fat magical technical manual. I love that the author took time to really develop the magic system, and knows the rules, but please publish that as an addendum piece for people who care to know all about how the magic works. Show me through the story that your magic has rules, limits, and a cost of use. Like a duck swimming on cloudy water, I want to see the smoothness and beauty of the magic and not the furiously pumping feet propelling it forward.
I want fewer coming of age books, I get that it makes it easier to world build if a MC is an apprentice that is learning about his/her world. I'd rather see a MC learn about the world by nearly getting eaten by a grue in the darkness, than some wise old master telling the MC "Don't go out in the darkness, you're likely to be eaten by a grue." I know there are stories out there like this, just want to see a few more of them.
I like stories with intrigue and behind the scenes manipulations, where the world keeps going outside of the POV. One of the things that bothered me about some of the older fantasy archetypes was that the hero goes on the quest, defeats the villain, and becomes a benevolent king/queen. But, would they? I mean, some farmer comes out of nowhere, finds an epic magical sword, defeats the enemy and no courtiers have been manipulating the situation so they can control this kid? Maybe that flirts a bit with the grim ways fantasy has been heading, but I like layers and layers of plot. Hence the need to have them in big fat books.
ETA I'm now calling layers and layers of plot, a plot lasagna, or plotsagna.