It is what people wanted though, from Facebook. Most people, including you and I, connect with friends through DMs in various apps, WhatsApp, or an equivalent group chat messenger (iMessage, etc.)

Facebook has become a lot like TikTok because that's what people want from an app that has a feed. We, en masse, don't engage with a feed of just our friends' posts (FB actually has a friend's feed which gets relatively little usage). When we open a feed-based app, we want the long doomscroll. I do think your restaurant analogy is apt. I mean nutritious food is healthier for people, but a miniscule number of restaurants serve such a thing, and none do which aren't trying to fill a small niche in the market