I think you're massively overblowing the nika fruit.Functionally the Nika fruit is literally just an awakened Gomu Gomu no mi. He doesn't gain additional powers aside from stretching more freely and affecting his envoirment. The backstory is a bit iffy but we know very little at this point and just who or what being Joyboy exactly means.

Obviously Luffy will in large part be the one to solve most problems but yo know he's the literal main character and has done exactly that since the start of the story.

I would have prefered the reveal of the gomu gomu no fruit to be something different but you're being a massive drama queen because half the shit you're crying about is just headcannon at this point.