Does anyone else get the sense that health research is flawed because the scientific process struggles to be holistic e.g. changing multiple variables at the sa

Does anyone else get the sense that health research is flawed because the scientific process struggles to be holistic e.g. changing multiple variables at the same time is not commonplace or even really realistic? Sometimes I read these studies and it feels a bit like someone reverse engineering a car without knowing what a car is supposed to do. Like - if you don't use oil, the engine is preserved quite well, unless you rotate the wheels, then it gets ruined, but only if the clutch is engaged. But then we do a study, we hold the clutch position constant, say it's disengaged, and then rotate the wheels at different speeds, and find that it doesn't make a difference, and publish that, and then it makes its' way into general understanding that you don't need to use engine oil. People seem to want to seperate the effects of diet, exercise, social interaction, etc, but I don't think this is possible in a complex system like a human being. They all need to be balanced.