“Indeed. But does that mean that what they say is definitively how the Torah wants us to behave?”
Even if it can’t be asserted definitively, it is definitively better to trust their judgement of how the Torah wants us to behave than to trust our own judgement on that. They are much more likely than us to be correct in knowing how the Torah wants us to behave. And if you think they are wrong in advising what the Torah wants, in all likelihood it is us who is wrong.