Actually, not so much as you seem to think. You're speaking of gross structure, and that's actually quite similar across the population. Not so much at the detailed level. People respond differently to medicines. People have differences in how they injure themselves, what gets tighter/looser/less pliable when range of motion is restricted, and what exercises work on them for recovering.
EDIT: By the way, by your words above, vehicles are much the same: motor, brakes, wheels, seats, check. But you can't tune a semi truck using a motorcycle manual. You probably can't tune a Volvo using a Saab manual, either. Heck, you probably can't tune a 1995 Honda using a 2015 Honda manual.