There’s not enough information given in Revelation to know what the prayers of the saints are or who they might be for.
You're right. That's why the Catholic Church is not bound by the non-Biblical invention of "sola scriptura."
Apostolic succession enables to successors to the Apostles to TEACH the Church and allows tradition to play a role. This is what they Bible actually says in 2 Thessalonians 2:14.