Just finished the third season, and on the whole, this show is very "just okay" to me.
With the first season, it borrowed heavily from Steven Spielberg and Stephen King, and wowed folks with 80s nostalgia. To it's credit, the casting job is very good for the most part, and it's fun seeing the characters interact with each other. The second season was a retread of the first, but even less satisfying. Not to mention the addition of the other people with superpower; an angle that went over like a fart in church.
With the third season, it's more of playing up 80s flair and nostalgia, and we see our heroes battle another monster from the Upside Down. Moving the plot along hinges on convenience, corny dialouge is spoken in moments that are meant to be taken more serious, bad attempts at humor stink up the better attempts, emotionally charged moments meant to tug at heartstrings lose their spark, and many characters are left with nothing really to do other than fill up the screen and say something witty. (For example, Will was basically just there to touch his neck, which helped nothing.) Boy, if this show was really trying to be an 80s horror flick that most people either didn't watch or forgot about, then it sure did hit the nail on the head. It shares a lot of the same traits you'd see in one of those films, (but benefits from generally better acting, a bigger budget, and actually being watched by a lot of people) so kudos. It really does live up to its 80s fanfaring to that degree.
But hey, I'm a fan of bad 80s horror films myself. (Let me give you some suggestions to check out: The Wraith, Street Trash, Blood Rage, Nightbeast, Intruder, Pieces, Maniac Cop, Friday the 13th: Part VI, Slumber Party Massacre 1 & 2, and so on) I get it, not too many people invest time in wading through old bad horror films to find the gems they like (nor should they or be expected to,) so something as mainstream as Stranger Things may be the first or one of the first introductions into corny, thinly-written horror forays. I feel The Duffer Brothers have not really done much other than benefit from drawing from the 80s-horror well that was dug for them. When I watch this show, I have a feeling of, "I've seen this all before, and many times better. Why is this so great?"
But I don't mean to rain on anyone's parade. If you like the show, more power to you. The characters can be fun, and who doesn't like to see people battle other-wordly monsters? I just can't seem to dig the show as other folks do.
Lastly, go watch Romero's Day of the Dead because it's a great film, and it deserves your attention. It's the least you could do since you just watched a season of a show that was inspired by it.