Not everything can be done with a randomized controlled study. For some fields (quantum mechanics, volcanology, climate change, paleontology...) most studies can't be randomized, much less blind. This is also true of longitudinal studies: you can't fully control anyone's exercise and diet over months, much less decades.
Yet we want to do research in these areas. So we have to make do with what's possible.
True! But medicine just so happens to be one of those fields that lends itself well to RCT’s. Perhaps if the OP had reworded their statement to everything in medicine it might make more sense.
Yet we want to do research in these areas. So we have to make do with what's possible.