This year's San Diego Comic Con saw Marvel Studios return to Hall H, announcing the now titled Avengers: Doomsday will be directed by the Russos and will star Robert Downey Jr. as Victor von Doom. The former have proven they can handle the Marvel sandbox and could even bring order to the Multiverse, like they did with the help of physicists in Avengers: Endgame. Response to Doom has been mixed though, with only 20% of this site's poll voters loving it. As part of that 20%, I will try to explain why I think the move makes sense to me. Even if I already made my case once for the Kangs.
Why it works (or not)
It's no secret that it didn't work out with Kang and the MCU had to pivot to another villain. However, any villain needs build-up. Even Thanos appeared before Avengers: Infinity War. With limited time to establish a new threat, Marvel has chosen a familiar face: Robert Downey Jr. Seeing him as the ultimate villain immediately invokes a sense of ''oh shit, that's trouble'' and raises intrigue about his transformation. Given Stark's arc and morally ambiguous actions he made, it's not difficult to imagine how a character like that turns into a villain. Even if he believes he's the hero.
Like Tony Stark, Victor von Doom is an ego-driven technological genius. Downey Jr. already portrayed the ultimate hero. and it would be a real shock to Avengers and audience alike that the ultimate villain is wearing the same face. This grabs the audience's attention, but the Russos know that a narrative reason is what keeps them engaged. For example, this Doom (possibly the last Illuminati member from Earth-838 with a personal vendetta and his Ultron at his side) is playing mind games and trying to mess with the Avengers by replacing his scarred face with that of Earth-616's greatest hero.
Ofcourse, it's also easy to see this as an act of desperation. Reception to Kang and the MCU wasn't great, so a new route had to be taken. Recasting Kang would've been easy, but might not have generated much interest given the character's initial lackluster impact. Moreover, many fans have pointed out Doom has a rich, layered history that deserves more build-up. While the general audience (i.e. the real target demographic) might not care for this depth, they could still be distracted by Downey Jr. in role that isn't his most famous one. Especially if they're less familiar with the Multiverse.
What it means for Doomsday
Regardless of what we think of it, it's a choice by Marvel Studios we have to accept. I wasn't a fan either of the casting initially, but when I started thinking about the possibilities my hype skyrocket. Although Feige nor the Russos confirmed where Doomsday would be based on (since there's no comic with that name), it could be base on Time Runs Out, the prelude to Secret Wars (2015). The namechange could imply that this time around the story is told from the perspective of Doom. And why wouldn't they with one the most famous and versatile actors in te movie portraying him?
In terms of story, Time Runs Out sees universe after universe falling to Incursions. The Cabal purposely destroys worlds to keep theirs from being next, while the Avengers and Doom seperately look for solutions. It is Doom that discovers that the Beyonders are responsible, and uses their own weapon (a Molecule Man-bomb) against them to steal their power to create Battleworld and rule it as God Emperor Doom. Like in the comics, this twist could be revealed in Secret Wars. Doomsday itself might refer to these events, either as literal doomsday (incursions of the Multiverse) or as Doom's day.
In the movie, some adjustments could make this work. The Council of Kangs can take the Cabal's place, with Doom quickly defeating them to establish he means business. The rest of the movie could focus on the Avengers trying to stop Doom, unbeknownst of his goals. In the end, instead of facing many Beyonders, Doom faces only one: the Kang from Quantumania that evolved into the Beyonder in the ants' pocket dimension. While Molecule Man doesn't appear in the MCU, the Scarlet Witch could take his place as the bomb in Time Runs out, while Loki takes his place as the battery in Secret Wars.
So, these are just a few reasons I could see it work. There are still many aspects I haven't covered, including what Kang Dynasty was initially about. Regardless, I think Doom is a better choice and a quicker route to Secret Wars than Kang or the Beyonder ever was, and that Feige, the Russos and McFeely can make it work. Secret Wars always needed the complex Doom, so might as well pull him forward. And a phenomenal actor like Oscar-winner Robert Downey Jr. has the chops to make that a unique performance. This is only my perspective though, so feel free to disagree in the comments below.