Now that I've watched and had some time to digest the ending, I want to preface this by saying that I am underwhelmed by the season as a whole.
As I stated previously, the Duffer Brothers wrote themselves into a corner and they were either unwilling or unable to write themselves out of it following Season 4.
With all that said, I didn't completely hate the ending. I have a lot of criticism for it but there are certainly worse ways it could have gone.
Do I believe that they could and should have condensed it based on those criticisms, absolutely. The final battle in the finale is basically what the ending was revolving around and it truly did not need the entirety of this season to carry it.
So many elements just didn't carry through. The military subplot really falls apart here, as it becomes sort of nonsensical. We literally forget about Max and Vickie, as well as Erica and Murray because they aren't needed for the main plot. Which seems to be a lot of the final episode to be honest.
I appreciate the ambiguous but tragic and slightly dark ending for Eleven. I do feel that if any character absolutely needed to have some sort of elimination, it was likely to be her. That was the original intent for Season 1, and it really fits her character overall. I felt Mike's character got flattened from the end of Season 1 onward, and this season was the same but the exception was the DnD ending and the story he came up with for Eleven. It was a touching and beautiful moment of shared grief for those characters. The final battle was a bit clunky but also ludicrously short for the antagonists, I didn't need non-stop action but Vecna basically seemed invulnerable in The Sorcerer save for Will's powers, which did help here but the whole battle wrapped up ridiculously quickly for the character who's been murdering secondary characters for 5 seasons...
With that said, I think a bigger problem for this season was that season 4 essentially wrapped up character arches for every character. So it was difficult to extract any interesting emotional moments or sense of conflict from the characters themselves, and while it's understandable that they were fighting the big bad, some of the most interesting moments on the show came from the conflicts between these characters and the resolution therein.
I think Will's coming out was okay and important as a moment, but it could have been more interesting if the context shifted slightly and we actually had some real emotional stakes in addition to the sci fi world ending stakes. I think it was beautiful seeing his friends and family accept him but I also think dramatic television needs more the sunshine and rainbows, and you could still have made interesting stakes without it being about any of the main group not accepting him.
Overall I think it was a good, not great wrap up to the entire series - I will admit I got a bit emotional
over the final DnD session and the next set of kids coming in to continue the tradition, and I'm probably more inclined to be that way at the moment due to my own life shifts and growth moments currently occuring, but I'll still count it as a genuinely emotional ending for me.
At the end of the day, this series ran a long time. And while I don't think it quite stuck the landing, I still feel a fair bit of fondness for it and I would always recommend someone watch the first season if nothing else because it genuinely had a wonderful start. I watched the Duffer Brother's original sizzle reel today and that was a really cool look into their initial concept and the true love they had for the filmography of 80s sci fi and adventure.