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Doom fails on the "hated by fans" measure - he's got a lot of fans out there, and has supported his own book several times.
Both of them fail on the Character Focus measure - "Put into big scenes for no reason" doesn't apply.
Doom is, as you say, one of the Big Bad characters of the setting. He gets involved in things because he can, and because he's a sorcerer/scientist/monarch who's frequently caught up in Evil Versus Oblivion plots. Trying to destroy the world he and his nation live on will usually get his attention.
The Sentry may be a God-Mode Sue, but that gives other characters plenty of in-universe reason to involve him. And, as noted, he started out as a title character. Arguably mishandled since, but...
I'd say cut.
The Doctor Doom example reads more like complaining than anything else. Just from the first example listed, Doctor Doom was the villain of the 2015 Secret Wars both because it's a callback to the original event where Doom was one of the central villains, and because the event was a culmination of most of what Hickman had done at Marvel at the time, including his Fantastic Four run.

CreatorsPet.Marvel Universe has these examples which seem indicative of wider misuse. (Creator's Pet only applies to minor characters getting unfair exposure/favoritism as main characters are expected to get such exposure/favoritism, and that they're hated by fans as opposed to becoming big in response to fan demand.)
My issue is given how comic work I'm not sure how to define a character as too major to count. Normally I say if their name is in the Comic Book namespace, they're too major, but The Sentry entry gives a counterargument to that.
The Creators Pet cleanup thread has been inactive for a few months now, so I'm asking here first.