Probably not the case here, but I never understood why manga distributers don't commission for epilogue comics/novels if the fan reaction is negative enough. A bad ending massively reduces any chance of new readers or previous readers buying merch.
I'm guessing it's more of a cultural thing.
Band-aid epilogues or ret-cons are usually made for corporate IP's.
Mangas and the culture around it are very much author based, so much that they call mangakas "Sensei", which is for "master" rather than "teacher", so if the mangaka isn't interested in doing more, then its left like that... at least in manga, because we've seen adaptations that vastly diverge from original mangas, a lot of 'em due to public reception.
Of course there are issues like Toriyama's contract that pressured him into continuing DBZ after the Cell Saga, and now Dragon Ball is more of a corporate IP rather than a authorial work.
But, in general, the public in Japan wants the "sensei" vision as it is, warts and all.
Problem is... Being a mangaka fucking sucks, burnouts are so bad that is a guaranteed hospital visit every couple of months, it is a sacrifice that not even the self-destructive japanese Work ethic can sustain. And even if you reach success, due to the demands of the job, you are bound to not enjoy any of the fruits of you labour. Masashi Kishimoto, the creator of Naruto, said it took him 15 years after he got married to get a proper honey-moon with his wife, Kentaro Miura, author of Berserker, was very vocal about being miserable as a manga author, and regreted the fact that he never married or had children because he gave his life to a manga that now he will never finish himself.
So, it's no wonder that this new generation of mangakas are bailing when they reach success and money.
As a example, Demon Slayers had a rather cut short run, with a lot of climatic fights just being smooshed nto one big arc. It was said that the author left Japan and moved to the U.S, regardless, we haven't heard any new works from her in 5 years.
Gege Akutami will never draw manga again other than just doing storyboards, and I doubt Fujimoto will ever do any long term serializations, he will stick with one and done short stories volumes.
The era of mangakas like George Morikawa, the author of Hajime no Ippo, guys who devote their entire lives over a singular work to the edification of a icon, is over, Morikawa is a dieing breed.
Not that it is a bad thing, I don't want to see any poor bastard chained to a desk drawing till theirs bodies give out, but it is a shame that this sense of legacy seems to be lost in modern manga, if I'm being a bit too romantic about it.
