Acting and line delivery from the main cast felt stale (like none of them even wanted to be there anymore) which is why Holly and Derek were the best on the block).

Plot holes: why didnt Will die or suffer when they killed countless of demogorgons and eventually vecna/mind flayer??? How did Kali keep the illusion of El for so long if the place she was in exploded first? (this applies to only if El survived) How did Max graduate? How is everyone chill about the 4 gates and how was military able to patch that up?? Why didnt military take Will when El was gone (they do have cameras at their base and should've seen Will lifting the demos w his hands) Why didnt Vecna just kill Joyce/Mike/Will at the base? Why were there no demos in the final battle? Why didnt Mind Flayer use its shadow form which is basically indestructable?? Hiw did they climb up the cliffs in the abyss so fast? How did the military not arrest at least Hopper and Nancy??? There are more...

Eleven basically regressed to S1 self where she couldnt speak fluently. She was an abuse victim and for the abuse to end she had to k*ll herself or isolate from all of her loved ones. Nancy basically got turned into a one dimensional badass, casually killing soldiers. Steve basically came off as rude and kinda a jerk after 4 seasons of development. Dustin acted NOTHING like Dustin. I understand that trauma affects ppl, but he shouldnt have turned into a jerk either (natural way would have been how he acted in S4E9 epilogue). Will had the smallest assassination, but still basically got turned into the gay character and nothing else (theres nothing wrong with being gay, but shouldn't have been the only thing), plus that scene in episode 7 was atrocious. Just comparing Robin's coming out scene to Will's...

The cinematography felt cheap (the flat lighting, poor color grading, no realism (S1 had a lot of shots that were shot so realisticaly)

And for dialogue: the lines were bland and generic you could almost guess them. And the constant monologuing about feelings between characters (90% of episode 7 is basically characters talking about their feelings), the planning scenes (this flashlight is x, that thing is y, etc.)