Felicia suffers the same problem as Selina.
You could theoretically write fun stories about them. But nobody ever does, because they remain plot devices linked to the heroes whose books they debuted it.
Hell, I'd argue Felicia is even easier to write a mini, or even a book for, since she kind of has more going on for her than Selina does. You can write plenty of Black Cat stories, give her plenty of chances for love and friendship, give her goals and aspirations, and have none of it tied to Spider-Man in any way. Because Felicia does actually have a personality beyond "I'm a sexy cat lady and I'm here to fuck an animal themed superhero on a rooftop". Less people would probably care as well, since Peter has MJ, so it's not like they can get made about Felicia being used for other things.