While modern fantasy fiction, cannot be exclusively described as gothic, it definitely borrows some elements, symbols and details which make the novels seem gothic more often than not. Sandersons Mistborn and Sapkowskis The Witcher can serve as testaments to this theory. Fantasy is a very flexible genre; it can absorb other genres, it can melt into another genre, or ultimately it can mix with another genre. This gives fantasy authors a myriad of possibilities in their world-building stage.
Of course, while there are many aspects which overlap with Gothic revival novels, essentially, these terms cannot be used to identify with one another.
While both of these genres have their specific and distinctive features, their boundaries can become fluid, which allows inter-penetration to take place.
To finish up the study I would like to refer to Marilyn Butlers categorisation of the Gothic:
there is a contrast between the sublime and the beautiful;
the frail, young and fragile heroine usually falls in love with a nice guy;
gloomy and large elements belong to the sublime, the dominant emotion is fear;
there is a contrast between light and darkness.
These are some of the major characteristics of The Witcher. A good example would be Kelpie, the mythological horse, which oftentimes appears in the books, and finally gives in to Ciri: the horse is beautiful, but he breathes fear into the hearts of those who see him. Fear also accompanies Ciri throughout the novels, since she is being hunted down by the Wild Hunt, a mythological group of warriors commonly present in Slavic and Germanic folklore. And while the books are filled with supernatural, they depict the perversion which persists in the human world perfectly. War is constant, war brings on death, and death brings on disease and extinction not only of magic, but also of the human race.
Add about mistborn
Throughout the novels the readers cannot help but identify themselves with Geralt and Ciri (both books), fear for them, and experience their adventures with them. However, this is done in the safety of our homes, and thus we even enjoy the feelings of fear, without being exposed to the imminent danger. This, yet again, takes us back to the sublime.
The Witcher and The Mistborn, just like many acknowledged Gothic novels, such as Lewis The Monk, or Irvings The Legend of Sleepy Hollow, present their readers a mixture of folklore, yet are written from a new, fresh and contemporary viewpoint.
To best describe these books, would be to say that these are stories which take place in fantasy universes reminiscent of mediaeval gothic culture thanks to architectural designs, dark atmosphere, presence of despair, fear and terror, and of course, the supernatural.