Nutritional science is a great example of this. There are “thought leaders” spearheading different nutritional belief systems (ideologies?) that completely disagree with each other and all back up their claims with what seems to be recognised well-done science. And they all have a long list of real world success cases showing that what they are promoting works for some people. I have moved from one extreme to another, from vegan to keto, finally realising that there is no one-size-fits-all solution for everybody. You have to try different things (vegan/keto/…) and get the medical/blood tests done to see if it works for you. If your health improves doing X then you are moving in the right direction.