BMI is just meant to be used on a societal population wide level it’s not useful on an individual level. In a population of 360 million (USA) how many Arnold Schwarzeneggers are there going to be? For every man that has a high BMI because he is jacked there will be at least 20 men who have a high BMI because they are fat. So overall it’s a good enough crude yardstick. It’s not feasible/economical yet for everyone to have access to devices which accurately measure body fat percentage, muscle percentage, bone density etc.Not saying there isn't an obesity crisis, but those metrics are pure slop.
After putting on a bunch of muscle, technically I'm obese, but my waste size hasn't changed. Before I was considered quite healthy and now muscle means I'm unhealthy.
Trust the Science!