You're getting at the Münchhausen trilemma. You are technically right, so let's just pick a pragmatic and useful definition of root cause: the preceding event

You're getting at the Münchhausen trilemma. You are technically right, so let's just pick a pragmatic and useful definition of root cause: the preceding event or circumstance that is at right the level of abstraction and proximity where knowledge of this will be maximally helpful to people in similar situations in the future.