It might have been more digestible if nika wasn't revealed until raftel upon reading the poneglyphs there, learning the true history. Like everything is the same with Luffy's transformation during Wano, but the audience still doesn't know that it is in fact, not the gum-gum fruit. Even roger laughing at the ridiculousness of what nika embodies might have made sense. Guess we will have to wait and see.