This is the most comicbook thing ever, and you guys should chill out.
Yes, Marvel movies are bad lately, but the Infinity Saga is a masterpiece of cinema (with its very-high highs and mediocre-at-worst lows) that no one but MarvelStudios has been able to pull off. Maybe they can do it again.
Also RDJ is an amazing actor and he will very probably do a brutal job at making us all forget Tony Stark even existed.
This decision was made with the money in mind, not cinema; this applies ti Disney and RDJ, so I don't expect a great production. Disney was desperately looking to bring the original cast back somehow, and RDJ has previously talked shit about his Marvel movies...
I'm not into comics, but I have read something about wolverine. The reason I avoid comics is exactly the same problem the MCU is facing: stories don't really have an impact: theres an infinite number of universes they can write about, and even in the base timeline, they bring back dead heroes; what's even the point?!
I've read/watched some content from people that would be more knowledgeable about comics/DC/Marvel saying that that's actually one of the issues comics have been facing: their audience loves X or Y character AS IS, and they don't allow it to either develope beyond what has been written, or don't want to see him/her retire/die...
I don't know if this is the true state of the industry, but watching the MCU struggle makes me believe it does: they brought back RDJ because they can't think of a solution to the hole they dug themselves into.
I hope they don't try to tell his origine again; we've seen it already. There are plenty of great actors that could've been Dr Doom, but nooo. This is just a money grab to me.
Hopefully he does take his mask off and they acknowledge it's some variant of Stark.