Tor and Nostr have one fundamental trait in common: redundancy. Nothing else matters for my analogy. Any system making use redundancy is worse off when the user or designer of that system attempts to distil the available components to only the most robust and reliable. Reducing the number of components can never make the system harder to break, no matter how high quality and well selected the remaining components are. Trying to find and select only the best relays is a complete waste of time, just like trying to prevent people from running Tor nodes unless you are confident they aren't keeping logs. They are identical in the way that matters.