rob: Ikkarei Emunah is not a straw man. It’s important here. The Rambam says that we cannot Pasken disputes in things that have no Halachic relevance (what you call Aggadita). Ikkarei Emunah are Halachically relevant and therefore can be Paskened.
And there is a tremendous difference between saying “We can’t Pasken disputes in Aggada” and “we can’t Pasken by Aggada”. Namely, the difference is that one is Mach’chish Magideha and one isn’t.