Part of it is the time suck, but a lot of it is the way that it perniciously invades my life. People invite me to parties. Oh, you're overseas, well here's the ONLINE LINK to buy stuff! Here are invites to 553 Lula Roe Pop Up Parties! Or how it spies on your search history or tells people what things you've read and liked that other people have posted. Though I try to be fairly apolitical on there, if I like an article and it throws it into someone's feed, they'll know what I was reading. That seems overly invasive. Etc.