There is a lot of research on how to estimate causal effects from data.
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
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