I used to read a ton of manga and 50% of the books I owned were manga (vs 35% american novels, 10% nonfiction books, and 5% notebooks with original writings). Now I've slowed down on reading manga because I can't find anything new that I like.
The same thing happened with anime. I watched a ton of anime growing up, but now I can't find anything I'm interested in (and what I am interested in a tear through so fast I'm almost immediately looking for something else). The thing with anime might be because I don't want to watch it pirated, and I can't afford a Crunchyroll subscription, so I'm limited to what Netflix has. 