The same happened to me. First, I started unfollowing people I don't interact with in real life anymore, after that, I unfollowed people I care about but who posted uninteresting things, then, I noticed there were tons of irrelevant Facebook pages in my timeline (pages I've "Liked" a long time ago maybe because I saw a good post from them or maybe the page's name was appealing) so I unfollowed all of them. I used to check Facebook several times during the day, now I check it two or maybe three times a day, because my timeline is almost empty. After several tries of quitting by deactivating my account, I think I finally found a good way to quit it, and maybe I don't even need to totally deactivate it since it doesn't absorbs my time anymore.