Then again,
one never sees a forward angled grip.
Training matters, but so do ergonomics. If you disagree, try flying a Piper Seminole in IMC conditions. Whoever thought it was a good idea to put the manifold pressure gauge where you have to look under and around the control yoke to see it deserves a kick in the jimmy. It's no fun, even for guys with lots of hours. (Note: Airline transport pilot rated former Naval Aviator, with commercial and private jet time as well.)
(This matters because it means every time you make a power adjustment, you have to take your scan off the instruments that tell you aircraft attitude, performance, and navigation data. Really, really poor placement.)
Despite training, my little cousin tended to short-stroke a Marlin 336, resulting in cartridges lodging behind the loading gate. His arms weren't quite long enough to operate it reliably. Is the 336 a bad rifle? No. Is it a bad rifle for him? Yes. Next time I take him out, he'll use a short action bolt, most likely.
Ok, so I'm in a handgun forum talking airplanes and rifles....
The point is, though, that training can overcome a lot of ergonomic issues. There may be times when it has to do so. However, when choosing a handgun for myself, I want something that feels good in my hand, that points naturally for me, and that operates in an instinctive manner. This means I can manipulate slide stop/release, safety/decocker (whichever, I have both), and magazine release with my primary shooting hand. It means the grip is comfortable, and lends itself to my hand finding the same shooting position nearly automatically on the draw.
Prior training and experience can bias the way one "naturally" points. In that sense, ergonomics can be impacted by preconception. However, my hand shape and size doesn't change. The angle my wrist feels most comfortable at is really a range, but it would be possible to design a grip outside that range.
On the bright side, most firearms with truly poor ergonomics tend to fizzle out rapidly; either that, or the manufacturer recognizes and corrects the problem relatively early in the production run.