I agree with your overall message but in this case I would like to point out one thing - a lot of fad diets were first adopted by people and then researched to see if they are helpful where as Fodmap has been specifically researched for the gut and only after it has been shown to be helpful, its now being recommended by doctors.

Obviously you should talk to your doctor before adopting the diet. It may not provide all of the nutrients that your body needs and its normally only recommended for 3 to ~6 months. Its may also not work well for some variants of IBS / IBD / other gut issues and may even be a detriment - so talk to your doctor.

Personally its been helpful for me. A lot of people also may not need to do fodmap and instead just do a elimination diet. For example you may not know it but may be suffering from lactose intolerance or gluten intolerance and so on. Probably easier to try that first as well.