I also dislike the regular overuse of the word "overated". More often than not its just a way of saying "I didn't like this as much as everyone else did", which doesn't make something overated. I've seen a lot of comments calling HoHH overated or worse even though I think its probably the best haunted house story of the last 20 years.
With Stranger Things its broadly popular because it's fun and full of nostalgia. This series has a lot of different monster film influences. This season I noticed a lot of The Thing, The Blob, The Terminator, and Invasion of the Body Snatchers. Which means there is a lot for me to love personally. It doesn't take itself too seriously either which makes it pretty easy to watch.
It's not my favorite show but its impossible for me not to enjoy the hell out of it. It's feels like its specifically created for someone my age and with my interests.