Beat me to it!
210lb (6ft1, not overly fat, stronger than most MTBer, dashing good looks) me on a 35lb bike is fine. But it's going to feel heavy AF for a someone who is 140lbs.
I also know that at my "SLX not XTR" level budget I need to favour strength over weight when making component choices, whereas someone who is lighter might not.
Where things get tricky is where you have someone who is quite slight, rides hard/clumsily but doesn't have a big budget. So teens then...