I love variety in reading and writing. The former inspire ideas for posts and stories (and the wider you cast your net here the more opportunities you have for being inspired. Literally keep an open mind and feed your mind well with wonderful material from other writers!). The latter keeps me on my toes. I love meeting the challenges of flash fiction and short story writing. I love meeting the challenges of non-fiction writing too.
But there's nothing wrong with sticking to one genre if that is what you prefer to do. So how can you bring variety in here? The crucial point is to enjoy what you write, whatever it is you go in for. If you're bored, that will show through in your writing (and I think will eventually lead you to stop writing altogether). For story writers, it is all down to characters as you can come up with so many combinations of characters and situations to write about. For me, a story is all about the character. It's then fun to find out what happens to them.
For non-fiction, I look at themes that interest me and write articles and posts around those. One obvious theme is writing. I love reading and writing about writing (and I enjoy sharing tips I've found useful. I am grateful to authors who have likewise inspired and helped me here. One of the loveliest things about the writing world is, with few exceptions, it is a supportive one. You learn something, share it, someone else learns, their writing benefits and overall literature benefits too. We will always need a supply of writers across the genres and age ranges).