This is a central point in the new book Outlive by Dr. Peter Attia. RCTs are great, but realistically we're never going to have long-term RCTs that give clear evidence on prevention of the chronic diseases that will probably kill most of us. A long RCT might measure the effect of a certain intervention over like five years but we need to think in terms of decades. No one is willing to fund those studies, and even if funding wasn't an issue the evidence would come too late for those of us alive today. So, we have to rely on weaker forms of evidence evaluated in a cost (or risk) versus benefit framework.

https://peterattiamd.com/outlive/