Oda has greater plans with him.
THAT is why he has Nami basically downplay him word for word the chapter, have him wrecked by base cat, and show the only way he has the balls to fight back/not run away is if he thinks he is literally hallucinating? Oda has "greater plans" with him?
Usopp is just never changing his character, no matter how much people wish for him to do so.
Even after Elbaf he will be the same coward he has always been, and Oda at BEST will have some giant give him a pep talk about "only those who feel fear can be truly brave warriors of the sea for facing that fear" ignoring the fact Usopp DOESN'T do that and just runs away/quakes in fear/cries to himself in sheer terror hoping somebody stronger will rescue him.
This guy will NEVER have a moment like Sogeking again. Its fucking over okay? And even if he DOES, that wont make up of well over a decade of being a total disappointment with character REGRESSION rather than development since Pre-Skip.
But from what Oda has shown me thus far with how HE writes Usopp? That lying scaredy cat is not getting Mjölnir, he is not gonna overcome his fear, none of that hype shit. Usopp fans MAYBE get a big speech out of him if you are lucky and no more.