This likely varies from author to author. I have some trouble with straight-up mysteries and standard romance stories, for example, and honestly am not sure whether I handle action well or not, but won a (very minor) award for a horror story once, and a humor piece got at least one class at my college to discuss it for about three times longer than it took me to write due to a philosophical twist to it.
For me, fantasy, especially "high" or "dark" fantasy, is the easiest, followed closely by the conglomeration of everything that is the modern superhero story (equal parts mythology, adventure, fantasy, science fiction, romance, slice of life, and sometimes even horror).
Straight up science fiction may be the toughest for me, as I tend to revert to pulp tropes or pull in fantasy elements whenever I try, though my Western/Sci-fi/Isekai story will at least justify it ... eventually.