It would if people could stick to the protocols in the studies as designed. In practice RCTs only enable us to estimate the effect of the _offer_ of treatment (

It would if people could stick to the protocols in the studies as designed. In practice RCTs only enable us to estimate the effect of the _offer_ of treatment (the intention to treat estimate) rather than making a direct causal estimate of the treatment itself. Missing data is a particular source of bias in this regard (if people dropped out, you can't know why or the counterfactual of what you would have observed had they stayed in the trial).