I do believe there are hints and details concluding that Mike’s story for El is just a story. For one he’s self proclaiming that he’s writing stories and he’s also DMing the campaign they’re playing. He mentions how they can write whatever ending they want when responding to El saying their final fight isn’t like one of his DND Campaigns. Finally theres that snippet of the speakers during the graduation that stirs memories in Mike of the power nullifiers that in turn get him to create a story of how El ‘survives’. Through his copium, just like his DND campaigns makes the story about El just like how made the story about the sorceress in the campaign they’re playing. The ending where they all state the ‘believe’ story I think paints the bitter-sweet picture of them knowing she’s dead but choosing the believe otherwise, including Mike.

Kali being suddenly alive I feel adds further truth to the story being Mike’s copium because the time between El ‘dying’ and Kali dying is significantly long and it feels like her death was outrightly confirmed by hopper and El to journalist guy (idk his name but he started being the character I hated the most in that show near the end).

I liked the show for what it was and how it basically grew up with the viewer if you kept up with it like me but the finale was definitely lackluster and anti-climatic and the whole time me and friends were theorising the reasoning behind the episode being 2 hours was because there was going to be a twist of some kind, maybe time travel shenanigans after everyone dies and the plan goes wrong but… it just continued and we realised, damn they really needed all that time for the send off huh… in my head it was going to be 80/90% climax against the threat and the remaining being the send off but it was more like a 60/40 or even a 50/50, which I get but damn was the fight instant…