After a little time to digest, I'll share my thoughts, with spoilers:
I am not necessarily crazy about all this multiverse stuff - it makes the movies too complicated, and I say that as a comic book fan. Movies are a different animal than long-form serialized stories that play out over years and decades. Anyway, and not surprisingly, the MCU has handled it well - very well. They have that golden touch and the movie was still quite enjoyable.
I was the only one in the theater who was not cheering at the introductions of certain characters, mostly because this WAS NOT THEM. The Illuminati is a concept from the comics, an outright terrible one. It's basically "heroes" doing the wrong things for the "right" reasons - however that never works. The "ends justify the means" approach is the antithesis of what superheroes stand for. "Making the hard decisions?" Doing the right thing is never a hard decision! And yeah, this concept has basically completely ruined Marvel Comics. So, here we have beloved characters set up as some tyranical council, lying to the world, controlling everything - make no mistake, they are EVIL. I cheered when they died - go Wanda! Nothing good comes from a group like that - I mean, anyone with a throne room like that is up to no good, no matter how much they think they are in the right. When "our" Dr. Dtrange called them a "clown show" I was so happy that the filmmakers get it - they know that it's a bad thing, and hopefully the Illuminati will be relegated to one weird, dystopian world in the multiverse.
But, that also led to one of the best lines in the movie, spoken no less by my most-loathed Charles Xavier of all people: "Just becuase someone has lost their way, doesn't mean they are lost forever." Man, what a great line - and trust me, Xavier int eh comics does not believe that anymore. They've made his so twisted and gross. That's why it hurts me so much sometimes - I used to love these characters, but they were all destroyed through years of bad storytelling - but the MCU may yet be their savior! It's incredilble how well they handle the material.
To wit, this whole movie is about doing the wrong things for the right reasons, from the moment the alternate Stephen treis to take America's powers. Even our Stephen had to dreamwalk to help his friends, and he paid the toll for that, but in the end he made the right choice. Only through that action could he save the world. So that's a good message and a good example of what these chracters mean. They do need to lose the weird thrid eye though - it's very unappealing and gross. I get that it was a cost, some kind of corruptuon, but I would rather it be visualized in a different way.
Wanda as the heavy was a surprise too. It took me a minute to even understand that she was. But, was she really? I always expected that she was being puppeteered, but perhaps not. Is she lost forever? I guess we'll find out eventually.