[strken]

What do you mean by "weight alone"? Even BMI is kg/m^2 rather than just weight. Do you mean total body fat percentage isn't a metric of health, or BMI doesn't closely track BF%, or literally that weight isn't a good metric?

Sorry if this is nitpicky, but responding to the claim is difficult without defining it precisely. For example, see this figure from a study comparing BMI and BF% in Greece: https://www.researchgate.net/figure/BMI-versus-body-fat-perc.... You can see that BMI incorrectly says a lot of people are healthy when they're obese in terms of body fat, but if you don't agree that body fat is a metric of health then I'd first need to convince you of that.

Edit: I'll also note that in that figure you can see the number of people who are incorrectly labelled as obese by BMI but not by BF%, and it's much smaller than the other way round. BMI tends to make your population look healthier than it really is, whereas most people who say BMI is flawed are making the opposite argument.