I'll tell you what was inauthentic, the mention of The Smiths.
They live in a small Indiana town in 1983, in Stranger Things.
In late 1982 The Smiths were recording their first demos. Their first UK release was Hand In Glove in May 1983. Their debut LP came out February 1984.
They are a peculiarly English band, and although I'm sure a handful of NY cool kids loved them from the outset, there's absolutely no way that a little town in Indiana knew about them in 1983, not a chance whatsoever, sorry. Generally, it took the US a while to get onto the Smiths, and although they may seem like all the Portland types love them now, it most certainly was not the case in 1983. It's not like they had the internet, Spotify, YouTube, etc. Unless David got a visit from a Mancunian distant family member, no chance, no chance.
This is by far the most glaring historical inaccuracy in the show in my considered opinion.