I swear to god, some of y'all would make me believe media literacy is goddamn dead with your takes, we legit got all the hints as to why Gojo is like that and you still manage to either forget them, since some are a long way back, or straight up miss them.
His obsession with perfection has always existed from the very beginning, him going through unhealthy practices to reach the result he wants, not wanting to trust others with work he can do himself, his tendency to tunnel vision when too engrossed into things, etc, every single "flaws" he has are there in this arc. And since now he added another goal of "Blowing the mind of the author which never praised any adaptation of his work", it's no wonder Gojo is going through so much.
People have to realize that Gojo is a goddamn craftsman first, he does cosplay to expand his horizons, him wanting perfection out of his work is something that is pretty much natural to him.
Hell, you can even see his Gramps knowing what Gojo is currently going through, being proud of him for finally reaching that point in a craftsman's life where you got a work with which you are so obsessed with that you yourself become a mess due to being unable to reach the image you have of it.
And you can bet that Gojo will finally find the light at the end of the tunnel of his obsession by going to the storage room his Gramps gave him once he finally remembers it exists, which i bet will be next chapter or the one after that.
The entire slow burn we are going through is to to put emphasis on how much Gojo is struggling with this work, to show to what length he is willing to go to create what he would consider a masterpiece as, unless he would see his work as such, he won't ever show it to anyone, especially since it is the first work that Marine didn't ask him to do but he himself decided to do, which adds another layer on his mind for wanting it to be perfect.
Also, as much as i can agree with people saying he should ask for help, he already tried relying on other professionals in the cosplay sphere to no avail since they don't know what he wants either, and while he could also ask his Gramps, i am willing to bet he forgot about him since he is too focused on it being "cosplay" and not "Hina Dolls", which in his mind is two different kind of craftsmanship, even if they share common ground so until Gojo breaks out of this mindset that the two are "different worlds that can't be mixed together" thanks to the storage room, that's not happening either.
You truly have to remember that it's his Gramps that told Gojo that expanding his horizons would be great for him, and that would also include expanding his mindset to accept that different kind of crafts can mix together, and we saw hints of that when he did his first cosplay and had trouble with doing "clothes for humans".