The darker theme in the start is that Doc sure seems like he was trying to unalive himself, and take Marty with him...

He drove the DeLorean straight at himself and Marty without knowing for sure it would work. The flaming tracks frame the two of them perfectly. Pretty obvious, actually...

An adorable side character in a comedy movie was intentionally written by the biggest movie studio in the world to mock a guy no one had heard of until the accusations started flying?

Hard to imagine...

So now all we have to do is explain why Marty's family still live in the same low key house together (despite being relatively wealthy)... including his older brother who is a successful business man.

Only the NAME Demogorgon shows up in Stranger Things. The creature with that name on the show has nothing to do with the Demon Lord in D&D.

Also, Demogorgon showed up in Gygax's Gord the Rogue series long before Salvatore hit the shelves.

I was going to make a comment about Flagg reawakened elsewhere and was instantly perceived as a deity by those around him.

It's almost like the writer of the article just watched the mini-series (hopefully the first one) and assumed it was faithful to the source material.