Well cutting system I suppose. I am not easy to fit with modern patterns. Really simple and obvious reasons- modern patterns are no better than vintage or cutting systems of different eras.
They are all designed to fit a single (or narrow range) of body shapes. They just are all different shapes. Mystery solved.
Right now it’s a low separate bust, oval shaped waist and hips, and no arms. Well okay so sometimes you can see that there was an attempt but modern armscyes are designed to sit flat while on a form.
So it’s not that we have “flaws” it’s that the patterns are designed for a single fit type. And it gets scaled up and down in a way that doesn’t reflect human bodies.
Having finally worked in bias on a large scale, and french bias, and also of course all those 19thC systems and I have gone earlier in research but mostly worked my way through all the early tailors manuals… you pick up on how to work with fabric for an idealised form, and what can be achieved across different shapes, and what was actually used to adjust to fit.
But I really want to get one of those brass drafting machines.