Dr. Doom is the best villain of Marvel in comics. If he's going to appear in Marvel movies, he should have his own character and personality, but now it's just RDJ wearing a doom costume. Also in comics, Dr. Doom is not a variant of Iron Man, nor is he related to Iron Man in any sense. I'm kind of sceptical they're going to ruin the Dr. Doom character, but I think they did not have other options, as Marvel is going downhill since Endgame, and after Jonathan Majors messed up, they really had very few choices to make the right decisions so they made a safe bet with rdj.