The simple combinatorial explosion criticism feels reductive to me. It's exceedingly unlikely that a single "self-replicating RNA molecule" formed independently by chance and then propagated.

Let's say that you have some RNA soup with some ribozymes some of which weakly encourage some reaction involving other RNA molecules. The occurrence of a cycle of reinforcing reactions might be sufficient to build a crude evolutionary ratchet.

In fact the "cycle of reactions" perspective feels a bit more robust to me since it allows for the proto-replication process to take place over a longer period of time and over larger areas.