But in essence this idea is not that different from the Gra that the only source of halacha is the gemara itself. דינא דגמרא the law of the gemara is what determines halacha not any posek even rishonim.

In fact most authorities thought little of books of halacha. The Maharsha said people that decide from the Shulchan Aruch are making a terrible mistake and it is proper to rebuke them.  Shlomo Luria [the author of the yam shel shelomo printed in every shas ]even went to far as to critique the Rambam for even writing a halacha book.