Here’s what I consider as must haves:-
Interesting characters. A fantasy cannot work if your characters don’t have depth to them. Give them a backstory, give them strengths, weaknesses, flaws, a personal touch to them.
Creativity. Tropes in fantasies don’t really attract anymore imo (this is a personal opinion). But the genre is literally FANTASY, it can have absolutely anything going on. Authors should take advantage of that.
Attractive visuals. Fantasies need to have eye-catching visuals. Period.
A central plot. What are your characters doing? Why are they doing it? What do they stand to lose/gain? Is there a main villain? Is it a journey of discovery?