Something About Halakhic History That Seems Obvious To Me But I Haven't Seen Anyone Say It So I'm Not Sure

Why Don't We Care About The Geonim That Much?

So back in the beginning of GSUFYO, the Facebook group for Jewish discussion I founded, one of the biggest sources of heartburn was the debates between followers of R. Jose Faur and people with more conventional views of halacha. I’m not going to go into detail about the specific Rambam-centric halakhic ideology of the Faurinistas, but one thing I do remember distinctly is being told “well, this is a halakhic opinion of one of the Geonim, which obviously cannot be argued with by people after them” and I was like “really? I thought Geonim were just rishonim”, which I, of course, received all kinds of invective directed towards me. Good times.¹

Thing is, they did raise an interesting point. Usually, the passage between eras of halakhic history includes a change in authority. Amoraim can’t argue with Tannaim. Acharonim can’t argue with Rishonim. You get it. The passage between the era of the Geonim and the Rishonim is the only one where, Faurinistas notwithstanding, it is not commonly assumed that there is a step down in the level of authority. Now, why is that?