I know these films haven't even been released yet, but I'll drop a SPOILERS warning anyway based on the trailers for Doomsday and potential rumors...just in case someone who is trying to avoid seeing or hearing anything about these movies can stop reading now and won't have to worry about being spoiled.
I'm not looking forward to Doomsday, nor Secret Wars. I know the hype for these MCU films right now is insane: RDJ returning; Chris Evans as Steve Rogers returning; and even the Russos are back. But the two main reasons that I will likely skipping both Doomsday and SW is because of...Doom.
1.) We won't get much (possibly not even any) of Doom's history with Reed from the comics.
This is a huge problem for me, because a lot of why Dr. Doom is who he is (and does what he does) in the comics is driven by his rivalry with Reed.
In fact, the 2015 Secret Wars storyline event from the comics (you know, the story that the 2027 Avengers: Secret Wars movie will be largely based on) is fueled by Doom's rivalry with Mr. Fantastic. Doom, during his creation of BattleWorld, literally wipes Reed Richards' existence from Sue Storm's mind, and Doom marries her instead. Not only that, even being the ultra-powerful God Emperor Doom, the Secret Wars story shows that Doom is still intimidated by Reed (and for good reason). This story does a great job of showing how much Reed affects Doom on a psychological level, and guess what? We likely will not be getting any of that, and that saddens me that we won't see on the big screen how much Reed makes Doom tick.
Honestly, how is it that we have a MCU version of the F4 who have a history with MoleMan, but no major shared history with Doom? That doesn't seem right. I get that the MCU has mostly been about doing things differently and subverting expectations - what with Aunt May giving Peter the "great responsibility" speech, female Silver Surfer, and whatever the heck Taskmaster was (I'm still miffed about that one)...but Doom is too important to the Marvel Universe; he should be done right, and not potentially end up being just a "Tony variant".
I'm not even sure that we will get a Reed vs. Doom rivalry at this point...and I know most of the MCU movie-going audience won't care. They are just blinded by nostalgia glasses and happy that their star RDJ is back. And that's really what Feige and the MCU want everyone to focus on, anyway - that RDJ will be gracing the MCU with his presence again.
Call it a desperate casting decision to have him play Doom or call it a brilliant one, but one truth still remains: that the MCU introduced Doom a bit early as part of their "damage control" since the MCU is undoubtedly struggling to keep people interested in their movies. But by bringing Doom in before they should have, they now have no choice but to axe any kind of history between Reed and Doom (unless they do a quick flashback showing that they did indeed have a history/rivalry, but it will likely be very short and unsatisfying).
The MCU could (and probably should have) played the long game and spent a couple of movies building up the rivalry between Richards and Doom, and even if that rivalry couldn't hold a candle to their rivalry in the comics, I would have still been pleased that they took the time to show that these two are destined enemies. I hope they at least have Reed be the one to defeat Doom in Avengers: Secret Wars so that there is some semblance of a rivalry between them, but I doubt it, as Reed isn't even close to being as smart as he is in the 616 Universe so I won't hold my breath for that either.
2.) MCU Doom will always live in the shadow of Tony Stark
Yeah, RDJ returning is exciting in a way, I cannot deny that...but him returning will only cast Doom in Tony Starks' shadow. Since RDJ is basically synonymous with Tony at this point, when people ever think about Doom in the future, it will be difficult to separate him from Tony (because you're insane if you believe that RDJ will be wearing the mask for most of the film).
Because when the audience inevitably sees RDJ when Doomsday is released, they will think "Tony" and "Ironman", instead of Victor Von Doom - who is arguably THE greatest villain in the Marvel Universe. We're talking about a villain who found a way to save the 616 Universe during the Incursions (another missed opportunity for a Reed and Doom rivalry, as Doom in the comics could gloat in front of Reed that he was the one who saved their universe from the Incursions), AND who made the powerful Thanos his bitch, by basically disintegrating him during BattleWorld.
He is a villain who is featured prominently as the "main threat" in many of the Marvel videogames, especially the beloved Marvel Ultimate Alliance. He is an imposing villain who can, time and time again, find ways to become a potential threat to the degree that sometimes it takes the combined efforts of superheroes to stop him. He is, as Reed mentions in the animated series Avengers: Earth's Mightiest Heroes, the type of villain who "gets what he wants". And what does the MCU want to do with him? Give him a connection to Tony Stark (again, he'll probably be some Tony variant with a traumatic past).
I don't care even if Avengers: Doomsday and Avengers: Secret Wars are both commercially and critically successful, the MCU took the one character I really wanted to see flourish on screen and be his own villain, but instead it looks like we will be only getting "Dark IronMan". Which is sad. They could have just had an evil IronMan from another universe (think Superior IronMan) who is involved somehow with the Incursions, instead of it being Doom. Yeah, it wouldn't have been comic accurate, but the MCU doesn't seem to care about that.