Ignoring instant messenger aspects, e.g. Facebook Messenger, then I don't use the majority of social media apps. I use Reddit a lot, particularly for sports, games, hobbies, etc. Also generally follow memes and subreddits with content I find humourous. I think that hobby based subreddits are the best ones are they are places that can help give good advice, nuture good discussion if properly moderated and help grow those respective hobbies communities. I try to avoid partaking in subs such as political ones as I think this aspect in particular is the worst of what social media can offer.
I have Facebook but also avoid using for similar reasons to avoiding political subreddits it. They're propaganda machines and rarely foster a good discussion environment. I also think Facebook, Instagram and the likes have a negative affect on how people view themselves, everything becomes a comparison to other people despite the fact that the majority of people will only show the best parts of their lives which makes them look artificially better than they are. On top of that, they're genuinely very poor at moderating their user base and you end up with problems like rampant pedophilia, scientific and political disinformation and vitriol (Twitter is horrendous for vitriol towards sports stars who have had a bad game).