IME, the UI/UX distinction is almost entirely artificial buzzwording anyway. People either define UX so broadly that it loses any useful meaning, or sufficiently narrowly that it's just stuff good UI people were doing long before anyone started buzzwording it.
Similarly, you seem to be using a particularly narrow definition of "designer" here, as if the only people designing web UIs come from print backgrounds and the only thing covered by "design" is aesthetics.
If you have a team where you have someone from that mostly unrelated background doing your UI design, sure, they're obviously not going to make great decisions. But even then, there's still no reason to assume your programmers will do any better, unless those programmers happen to also have genuine UI design skills (which they certainly could, but it's mostly orthogonal to their role as programmers).
Similarly, you seem to be using a particularly narrow definition of "designer" here, as if the only people designing web UIs come from print backgrounds and the only thing covered by "design" is aesthetics.
If you have a team where you have someone from that mostly unrelated background doing your UI design, sure, they're obviously not going to make great decisions. But even then, there's still no reason to assume your programmers will do any better, unless those programmers happen to also have genuine UI design skills (which they certainly could, but it's mostly orthogonal to their role as programmers).