What's your take on bmis? i know people who are more lean/muscle and are in the obesity range whereas im skinnyfat & "healthy" despite minimal muscle

Waist/height ratio: Bmi is an ok but not great measure. I prefer waist/height ratio. Waist circumference is a better measure. Men should be under 40 inches, and women under 35 inches. Measure waist at naval. If extremely obese, lay flat on their back, then measure. Whtr= waist circumference in inches / height in inches. People under 50 years old should be below 0.5 people over 60 years old should be under 0.6 people.

OverlySimpleShorcuts: Like most metrics commonly used for population statistics, not accurate/reliable for any 1 individual. Yet used as simple/cheap to collect (though flawed) data for statistical analysis of group trends. While sometimes helpful for seeing group trends; data can also often be misleading because simplistic/flawed; more bad raw data never creates excellence of cumulative data; meta-analysis an example.

BMI & body fat %.: The BMI reflects your weight with respect to your height, but as you suggested does not reflect body composition. People who are very muscular could have a higher BMI that would not be truly reflective of their fitness and health. Combining the BMI with a body fat percentage would greatly increase its accuracy.