Funny, everywhere else people would call a series that constantly finds new ways to use old material a series that cares about its lore, continuity, and the things that makes it special. Even Star Wars novels find ways to constantly integrate the ideas of the empire, and the Sith/Jedi conflict all throughout the timeline, because that is good writing. Even KOTOR 1+2, often considered the best star war side materials, did it. No well written series unvierse just tosses aside its key defining pieces. It would be like TES just throwing away the Daedra. Only bad writing allows such massive elements of a fictional unvierse to be tossed aside later.
They did plenty with it by tying it into the history of The Institute, and using their failure at FEV as the reason behind why they kidnapped Shaun in the first place. At the same time, they echo past lore, and show a fundamental basis of the series unvierse that people keep trying the same things over and over, be it forms of government, petty racism, or technologies, with the same results, aka "war, war never changes".
How is what I said in any way bipolar? do you even know what being bipolar means? How is constantly reiterating the fact that I didn't find New Vegas interesting, because its just repeated what we already knew, and didn't tie it to the overall plot of the game world, whereas Fallout 3/4 are new, since the super mutants aren't the like the ones in Fo1/2/NV, and it did tie its super mutant presence into the gameworld/overall plot, and are thus more interesting because of it, in any way bipolar? Iswear its like you only read every other sentence or something.
Go back and play Fallout 1
http://fallout.gamepedia.com/ZAX.MSG
"No. FEV does not retain unaltered original copies of the subject's DNA.
Only a virus which re-infected the subject with original DNA could reverse the effects. Additionally, there is no known way to remove the FEV itself."
FEV could be undone as far back as Fallout 1, and is exactly what Virgil does. Whats more is that he says he still retains some of the augments of FEV, such as increased muscle mass, and hes apparently no longer bald, so he is still infected with FEV to some degree.
He says he could possibly generalize the cure for other strains, but it may take decades. Also, if you side with the BoS, Lancer Captain Kells will agree to keep him alive because he found a cure, calling him an asset. Its very possible that by the time of Fallout 5 the BoS may be able to mass produce the cure and revert all the super mutants, or at least some of them.