DY: The Darchei HaLimud are based on Mesorahs that have a Makor in Shas and Rishonim. Whether it’s Pilpul, Brisker, or anything in between, the way it is done is based on a Mehalech the early Rishonim had in Shas, which they themselves received from the Geonim who had a tradition straight from the Amoraim. The early Rishonim and Geonim had direct Mesorahs to Chazal (meaning they could quote, Ish Achar Ish, who they were saying their statements in the name of). No one today can do any such thing. If someone had an unwritten Mesorah that they could quote who it came from and how that Mesorah was transmitted Midor L’dor then it would be different. A random person claiming an “unwritten Mesorah” that has no basis in Seforim but is a core belief in Judaism is an attempt to uproot Judaism, plain and simple.
To be honest, I’m not sure why you’re arguing with me here. You agree with this point. You just won’t concede because LF happens to be either right or not-so-wrong in this case. But if anyone else made any claim and had to back it up by saying it’s central in Yiddishkeit but have no Makor for it, you would tell them to join Shmuely Yanklowitz and Zev Farber and leave you alone.