I recently finished this 6 part series of what could be considered the most unique and confusing thing Marvel has ever produced (and I've watched WandaVision so it's saying something). I can't cite the source but I distinctly recall Kevin Feige or some Disney or Marvel big boss saying that the Disney+ shows won't be necessary to understand the overall arch of the MCU - either he was lying or he was lying. Loki might be the most important MCU production to date and perhaps our entrance into Phase 4. I'm not complaining though - the Tom's performance was incredible, Owen Wilson blew it out of the park, and the fandom's fear of how they would introduce the multiverse was done rather seamlessly. Here are some thoughts coming out of the series. Spoilers ahead.
The Marvel Cinematic Universe's interpretation of the Multiverse allows them to have an endless array of movies and tv shows without having much consequence, which is probably their exact intent. As they concluded a decade long process of continuing one timeline (both within the fictional universe and their production efforts), I'm sure a lot of internal discussion happened at Marvel Studios and Disney about next steps on how to be logical in their storytelling while maximizing profits. It's quite hard to keep an entire universe going with a set fan base that's willing to watch anything and everything you'd put out, as long as you don't piss them off with inconsistencies. Now with the multiverse in play and the idea that there are an infinite array of parallel universes occuring where different characters can take different shapes and sizes (therefore the same character being played by multiple actors and having other timelines not necessarily affect the "main" one we're used to), Marvel can theoretically churn out endless movies with the same characters and not necessarily use the same actors that now cost a billion dollars to bring together. I'm sure they'll have the occasional cameo appearances from RDJ and Chris every once in awhile for continuity and sentimental value, but I wouldn't be surprised if instead of a reboot, they will just recast these characters and call them a different universe Iron Man and Cap.
Tom Hiddleston and Owen Wilson were phenomenal in their performances - especially given how strong of a character Loki is in past movies and how much the Owen Wilson persona is ingrained in most Americans' minds. Not only did they play off each others' acting, but they were able to sell the idea that a Nordic god (frost giant!) was in a time controlling agency without being overly cringey. Anything that requires messing with time and fictional gods have a tendency to require a lot of explicit plot explanations, which could easily ruin the pace of the show or movie. The way that the two characters carry this out (also recognize that this is largely to the credit of the writers so shout out to them!) and allow the audience to buy into the idea of TVA is remarkable. This means even more considering the fact that this series basically delegitimizes the entirety of the MCU we're used to so far (did you see the number of confiscated infinity stones?) and it doesn't feel as sour as it should is great work.
I tried my hardest to shy away from Reddit during this series to refrain from reading accurate fan theories and therefore ruin what's to come. Based on my intuition and Marvel "expertise," I did expect the Time Keepers to be false identities. However, as my original source content knowledge is close to zero, I was very caught off guard by the true "villain" or the One Who Remains. If I recall correctly I don't think his name was explicitly mentioned (for those of you wondering it's Kang the Conquerer) so I had to do some Reddit and Wikipedia digging to understand who this was. In the little that I learned yesterday since finishing the episode, it seems like he's a very powerful and scary individual which are two very important prerequisites to be a villain (I miss Thanos). I envision multiple versions of Kang being the true villains of Phase 4 as he's already slated to be in the next Ant Man movie and assume he'll be built up to take the throne in the Phase 4 Avengers finale.
Overall, I'm very pleased with Marvel's handling of the multiverse and the transition they've had from the original Infinity Saga. One could argue that COVID actually did them a favor as people are actively ready to take on streaming content as well as return to the theaters. Please drop the Spiderman trailer soon.