First of all, I use Facebook in a similar way (dedicated email, sandboxed browser, external tracking disabled (I know it still tracks me internally), not entirely my real name, no mobile apps, all paranoia privacy settings on, don't really share anything). And I only signed up there a year or two ago. But Facebook absolutely helped my social (and even professional) life. Even if I can reach people by other means, it doesn't change the fact that they prefer to keep in touch with Messenger, we have our private group chats there. Facebook lets me keep up with cultural (art/music) events, and also local dev meetups. I have my current relationship thanks to Facebook as well (I met her in real life first, but we only started to hang out because I looked her up and added her on Facebook and we started chatting there). I even got my dream dev job accidentally, because of a Facebook share by an acquaintance. Buy/sell groups also got me a lot of good deals, including my current apartment.
That doesn't change the fact that, as a company, ethically, strategically etc. I despise Facebook. I hate their manipulative practices. Most of the information shared there is pure shit (but I can more or less choose not to follow it). Regardless, by not being there I'd be losing more than gaining.
Now, LinkedIn I detest even more, thanks to the unsolicited invites from strangers that I get to my private email, even though I haven't even registered there, and I have no intention of doing so.