If it's any consolation, you are correct about Dr. Doom in the first Fantastic Four movie. Having Dr. Doom be a sorceror-scientist who happens to be jealous of his college friend whom he also blames for his failure to restore his mother to life by necromancy and his hideous scarring who seizes an entire postage stamp kingdom and achieves tremendous scientific power but foolishly neglects to kill his dearest enemy until said enemy accidentally gains superpowers, along with enough friends to keep said sorceror-scientist from every triumphing, and indeed, merely foolishly tagging along as best frenemy, eventually to be called Uncle Doom...This would have been hard to fit into any movie, live action, comic book or original fantasy. Dr. Doom's origin and fixation on the Fantastic Four is a bloody mess, and the movie can't be faulted for not making a silk purse out of a sow's ear.
The proper way to work Doom into a movie would have been to have him established at the beginning of the film as the leader of the 'rogue' nation of Latveria whose threats against the free world are the impetus for Reed and company getting powers in the first place.
Like Vader, don't worry about a lengthy origin sequence in the initial film, just set up that Doom was a brilliant scientist/dictator who tampered with forces beyond his ken in a quest for ultimate power and was now hideously scarred. And now, he's convinced he's got it right and is going try again--only with the whole world at stake.
Doom's plan involves piercing dimensions and powering his invention with a new form of cosmic energy believed to exist only in a place called "the negative zone." So far he hasn't gotten there but it's only a matter of time. And the US and its allies know it.
Government scientist Reed Richards is the scientist tasked with stopping Doom. Reed is certainly up to the assignment. Besides being one of the most brilliant men on earth, he’s almost as familiar with Doom’s theories as Doom himself. And he’s practically obsessed with stopping Doom.
Reed has theorized that—if he can tap a small amount of the negative zone energy first—he can create a device (which he nicknamed the ultimate nullifier) that would not only prevent Doom from powering his own device but could--if safely harnessed--lead to an end to the energy crisis.
Unlike Doom who wants to open the portal haphazardly and essentially bring the negative zone to earth, Reed is trying to build a vessel (kind of like an interdimensional submarine) that can take a small crew and instruments over there to study and tap into the energy before it reaches earth.
Assisting Reed in his experiments are a team of scientists including his girlfriend Sue Storm and her brother, Johnny (a grad student, very bright, but a hothead who’d rather be designing race cars and chasing pretty girls like his hero, Tony Stark). They are guarded by Ben Grimm, a former fighter pilot who’s become Reed’s best friend.
The team is working day and night to set up the vessel but time is running out. News is coming out every day from their intelligence sources that Doom is getting closer and Reed is getting more and more obsessed with stopping him.
And then, the news they dreaded: Victor is further along that they feared. They’ve got no choice but to try and make the trip in the prototype before the shields are fully tested...and we all know what happens then
Once the quartet gets back to earth, establish the team of superheroes along the usual FF lines and then, when the time is right, send them out to stop Doom, since Latveria is too fortified for anyone but them to get inside at this point.
And now, the big reveal: Years ago, Doom and Reed once colleagues. Reed--as a young scientist--had assisted Doom in early (successful) experiments but backed away from Doom well before the incident that caused the scarring when he realized that Victor was up to no good. The group now realizes why he’s obsessed with Victor.
(Doom, for his part, doesn’t give a fig about Reed at this point. Reed’s basically a lesser scientist who—in Doom’s mind—couldn’t even shield an experiment properly [completely oblivious to them being two sides of the same coin in that regard])
The movie ends with the customary action scenes and Doom defeated, vowing vengeance against Richards and the FF for stopping him.