It's not just Facebook, it's social media in general. More precisely, it's infinite scroll, which has become a ubiquitous design decision across social media. I recently finally succeeded in developing a healthy relationship to social media, and it involved disabling infinite scroll where I could (using Hackernews, moving to old Reddit) and quitting the social media sites where I couldn't (mostly Youtube). I'm scared to touch Facebook, Instagram, or Twitter because the infinite scroll mechanism is so addictive.