Is there nothing between RCTs and "high-fives" to estimate causal effects? Economists seem to run awfully long journal articles if they all boil down to high fives.
And text books. "Causality" by Pearl about causal models in general. "Causation, Prediction, and Search" by Spirtes about how to learn the models from data.
For example assume the world consists of three random variables A, B, and C. If A causes B and B causes C (as DAG A -> B -> C), then A and C are correlated. But if the model is A -> B <- C, then A and C are not correlated. But conditioned on B, A and C are correlated in A->B<-C and not correlated in A->B->C. So you can falsify such causal models without an rct