I don't use Twitter or Instagram, I just don't see the point, and, as you point out, they are a time suck. I mean, I love researching and learning, but I don't have the time for sitting and being on line all of the time. I am on Facebook, and look at it way too much, but I don't post very much. I stay away from making any political comments, although I do follow some politically oriented things. I use it mostly to keep up with friends far away.
I find it interesting that my kids, who are in the prime demographic for these things, both think Twitter is silly. My older son had his Facebook hacked (he didn't tell me what happened, but I think his photos were used in a very inappropriate way) and has not gone back. Considering that he had 300+ friends and planned and orchestrated his high school reunion through Facebook, I am surprised. My other son has had a love hate relationship with Facebook. He was not on at all, until right before he finished his last tour in Afghanistan and was out of the military. Then, all of a sudden, last fall, he deactiviated his account. About a week ago, I noticed he was back on. I think this was related to the fact that he was getting his security clearance re-upped, so he has to appear squeaky clean.
You could spend all day looking at stuff, and it's really easy to get addicted.