I shut down my facebook account seven years ago. I'd noticed fairly early on that what I did there was basically marketing myself and some stalking. I also noticed I was poor in marketing and felt ashamed of myself. In consequence my interest in stalking / following others' marketing faded, and shutting down my account was the only logical action to take. I've never regretted it.
I have a smartphone, but don't use it except for texting and making calls. Since I have maybe 10-20 calls or texts a week, I usually don't take my phone to work. For me, email at work and a phone at home is enough for setting up appointments and leading a satisfactory social life. It's a great relief not carrying this nagging tracking device around with me all day.
I don't understand what's the great thing about smartphones. They are much less convenient to use than a desktop or laptop for most of the things I do (emailing, web surfing, software development). (what things are so important that need the mobility or the special devices not typically found in desktops such as touch, GPS, camera? Maybe if I played Pokemon Go or had selfie-taking or QR scanning addiction...).
I also totally hate when I have to share others' attention with their smartphones. Personally I've learned to embrace or even enjoy boredom, or watching out the window, or sitting in a bar drinking beer, thinking of nothing at all. I feel my head is working underneath, and I need the balance I get from doing nothing conscious. A quote from Pulp Fiction that I like: “That's when you know you've found somebody really special. When you can just shut the fuck up for a minute and comfortably share silence.”
However my big problem is dealing with computers at work, and sitting in front of them 8-10 hours a day, at work and at home. When I don't feel productive (most of the time -- I try to make good decisions in my software designs, and thoughts need time to settle), my time is spent randomly clicking links on news sites, HN and twitter (barely sending, mostly consuming).
I would really like to be more productive and consume less unimportant news. However knowing I'm not a genious I doubt that more isolation will improve my productivity.