Since you started writing, we’ve seen all of the tropes of science fiction and fantasy become parts of mainstream culture — and yet there is still a very strong sense of what is genre and what is not.
As far as I am concerned, there is only one essential division in the art of literature. It is either good or bad. Mainstream vs. genre is a false dilemma. I have read many mainstream works that are rather poor and a number of genre books that are truly excellent.
You can read more here.