Social media stuff I just tend not to reply straight away if I know I'm likely to be suck up into a long-winded convo. I have a couple of friends who tend to drone on a lot a bit, and when I see a message from one of them popping up I'll leave it an hour or two before I text back and by then they're hopefully doing something else and it won't be as long a chat. I'd obviously reply straight away if I can see it's urgent, but from these friends in particular it's generally just aimless gossip and fashion chat, nothing that can't wait.
Social engagements I'd rather not attend, I'll either go for a diplomatic excuse (prior engagement, or I travel very frequently for work and people know that, so I might say I'm away), or if it's a good friend doing the inviting I might tell the truth and tell them it's not really my thing.