How can one explain the notion of Torah She’Baal Peh when so many of the Mitzvot as interpreted in the Gemara seem to be deduced in so many different ways? If in fact it was not the traditions themselves but the power of the Rabbis as the leaders of their generations to interpret the Torah that validates Rabbinic Judaism as we know it, how can we relate to it as holy and authentic? Do we yearn for the time when we will go back to ancient Israelite practices or do we in fact believe that God so to speak agrees with the Rabbis and our current form of Judaism is therefore divinely inspired and commanded? Do we truly believe that what the Rabbis claimed was D’Oraita was in fact exactly as it was practiced since Matan Torah-i.e. that Tefillin looked exactly the same, people recited the Shema in the evening and morning, observed 39 Melachot, etc.?
As you said – we, the faithful students of Moshe Rabenu, truly and fully believe that the Torah we have is authentic as Hashem meant it to be and that what the Rabbis claimed was D’Oraita was in fact exactly as it was practiced since Matan Torah-i.e. that Tefilin looked the same, people recited the Shema in the evening and morning, observed 39 Melachot, etc. – there is obviously a development of halacha throughout the generations but the differences are only on the fringe of things – the main core of all Halachot is the same. That is what the Rambam meant in his eighth principal of faith – the WHOLE Torah we have today is the same Torah Moshe Rabenu received in Har Sinai; the written and the oral. The torah itself states that we should be listening to the words of the rabbis of all generations – in Devarim 17, 9 – 11; to say that the interpretation of the rabbis to the torah is the torah itself.