Yes and no. It depends on the person, they may lack the skill or they may not be playing the right Flute for them. Either way, they could get better on that Flute, but I think (which doesn’t mean much) they would get better faster on a Flute that played the way they liked.
Myself for example. I used to play a Rudall style Flute which I liked, but I always found myself over blowing it. Was it nessacarily the instrument, or my own lack of skill? I may never know, but when I started playing a Pratten style Flute I found myself learning new things and ultimatly becoming a better player. Is this always the case? No, it is just what happened to me. If I had stuck with the Rudall style eventually I would have been able to play it better. Although, the Pratten style helped me grow into a better Flute player. I find that I learn better when I dive right into something, not every body is that way. Some people may do better learning gradually. Which is why I can’t give a straight answer to the question.
My point was that it is very much the person that makes the Flute. Yet, at the same time one will do better on certain Flutes due to their physic and playing style.