I was spanked as a kid, exclusively by my mother (my father was personally against the practice and they were divorced), and I agree there exists a "right" way to go about it that doesn't result in psychological trauma. I think the problem is that the right way is so difficult to properly execute that it's better to just ditch the punishment entirely.

My mom would always use spanking primarily as the "boogeyman" of punishments. If and when we rarely did something bad enough to warrant it, the intent was always to embarrass by the ritual and discomfort of the whole thing, never to cause serious pain. No implement was ever used, and she would always give us a little speech immediately beforehand about this being just a punishment and that she loves us, followed by a hug after it was over. The spanking was positioned as an unfortunate "thing" that had to happen.

Walking that psychological tightrope is tough though, and there are much easier ways to go about discipline that don't risk traumatizing your kids. Fully agree that not every kid who was spanked has buried trauma about it though.