The Enclave being in the East Coast, being the same Enclave from the Oil Rig that decided to cross the entire country, is worse than the existence of Jet on the East Coast, but the former doesn't override any lore
I think Jet is worse. Enclave makes a lot more sense despite what is said and gathered from Fallout 2. Is it a good thing? Nah but it's better than just making nonsensical inconsistencies. Enclave is a shadow/secret government operation, having members in and around the nation's capital isn't a wild idea. Could have been a different shadow/secret govt agency or whatever. But Jet being a pre-war substance that Myron is now either lying about or used as a basis for a new drug that's functionally identical does what for the games? Allows us to have Jet everywhere? Yippee. At least trying to make the Enclave work for Fallout 3 has purpose as they're integral to the story that was written.
We can say the story should have been different than what it was, which yeah, it should have been. But reusing a faction for narrative purposes especially when it's plausible enough so that a canonical "readjustment" feels like it could be justifiable is better than just saying, "Yeah all that shit with Myron is bullshit or half-truths because we don't want to think of something else."
Both shouldn't happen, I agree. But I do think one way is a bigger middle finger to what's been established. If you're going to rework what's already here, at least give the new shit a purpose to trample over the old one.
Super Mutants are one that I think is more inline with Jet than the Enclave. They don't serve a lot of story purpose besides being enemies that don't have conversations with you and they are "distinct" enough from their West Coast counterpart that it feels like they should have been something else. They aren't from Mariposa, they don't know Grey/Master in any capacity, they aren't the same type of Super Mutant, so the only connection they really have is being FEV mutants of humans. I don't think them being simpleton barbarians with puke yellow-green hues really justifies having the same physiology and being named the same as the Mariposa mutants. Just make something else even if it was created with FEV, it'd be just as interesting on that alone and with some writing and exploration into the idea would be vastly preferable.
Enclave makes sense to me because in the Washington DC area, I can see why someone would maybe think they should use the faction that had the US President in it. Is it lazy? Yeah, but it makes a lot more sense than other decisions (or lack of conscious decisions) made.