Everyone else has covered this pretty well, but since you did ask me, I figure the polite thing to do is respond! D&D and other pen and paper RPGs have been on

Everyone else has covered this pretty well, but since you did ask me, I figure the polite thing to do is respond! D&D and other pen and paper RPGs have been on the rise since before Stranger Things, and I think ST making it a plot element might be due to that, more than the other way around. We've also seen a bigger push for some 'simpler' RPG systems that are a less rules heavy to try and entice newcomers to the genre. Fate has been the big one here, but others have stepped into the ring, and Fantasy Flight Games, which is a big name in the board game world, just released the Genesys rulebooks, which are based on their 'Narrative Dice' systems, which uses much simpler rules than a more traditional d20 style system. They had previously used it for their Warhammer and Star Wars RPGs, but Genesys is meant to be general purpose for whatever setting you may like.