I thought about that almost through the entire finale. Except for the ending bits, which I obviously liked, because a group of people just recently out of High School (Steve and Robin and the gang) with their real lives beginning is just bound to make me nostalgic and sad, especially when there's also the original kid gang just graduating. Found myself wondering: is a nothing finale like that really a good way to go out?
It's the most forgettable ending to a series ever, and it ends one of the, if not the, most successful - for better or worse - shows on streaming ever made. Honestly, they should have just replayed a mixture of NGE's original ending and End of Evangelion (mostly in Vecna's mind), with Instrumentality, err, sorry, the thing that is about to happen in the finale that our heroes are trying to stop, playing out in the background.
That would have been the best thing ever, and I don't say that lightly. Just follow that idea for a moment and see Kali (with better development and a better actress), El and Will as Asuka, Rei and Shinji for a moment. Just with psychic powers and monsters instead of genetically engineered alien hybrid mechs fighting Angels. It could even end with El and Mike washing ashore on the sea of the Human hive mind.
And yeah, the retcons? Not a fan. Worst decision ever. Totally unnecessary. The Upside Down was fine as a eldritch horror mirror dimension / Shadow Plane take.
The last 20 minutes are character sendoffs - the best part of the episode, by far and large.