the lack of Machlokes before Hillel and Shamai wasn’t due to there being Nevi’im who could Pasken, it was due to the fact that we had a Sanhedrin and thus could reject certain Shittos with finality
This much is mefurash in the Gemara (Sanhedrin 88b).
??? ??? ???? ?????? ?? ??? ????? ?????? ?????? ??? ??? ??? ?? ????? ???? ?????? ????? ????? ???? ??? ????? ?? ????? ????? ??? ???? ?? ??? ?? ???? ???? ???? ?? ??? ????? ???? ??? ????? ?? ????? ????? ?????? ??? ?????? ????? ????? ???? ????? ?????? ???? ??? ?????? ?? ???? ???? ??? ??? ??? ???? ??? ????? ????? ?? ???? ???? ??? ??? ??? ???? ??? ??? ??? ?? ???? ?? ???? ???? ??? ??? ??? ???? ??? ??? ??? ????? ????? ?? ????? ??? ???? ????? ?? ????? ??? ???? ????? ?? ???? ???? ??? ??? ??? ??? ???? ???? ????? ????? ??? ?????? ????? ?? ??? ?? ???? ?? ??? ?????? ??????? ?????? ????? ?????? ???? ????? ???? ?????? ?? ???? ???? ??? ??? ??? ?????? ????? ??? ??????? ???? ??? ??????? ???? ????? ?????? ???? ???? ??? ???? ?? ???? ??? ?????? ?????? ?????? ???? ???? ?????
Note how it clearly says even before the students of Hillel and Shammai there were disagreements which were ultimately resolved by vote.