I think it's OK to start out as non-technical product manager but over time they should pick up some technical knowledge. Some product managers refuse to learn anything technical which doesn't work well in the long run in my view.
Same for developers. They shouldn't just wait for requirements but also understand their users to some degree.
In the end engineering and product management should develop some competence in the other's area. Otherwise communication is very tedious and error prone.
This is an interesting point. The first several years of my career, I was an engineer working on low level operating system stuff. I later switched to product and my technical chops really helped me earlier in my product career. As I got more senior however, the business, strategy, and product vision components of the PM role became more important and my technical skillset was less "directly" useful. It was more helpful in getting me trust with senior engineers, and therefore transitive trust with executives (because eng directors are often the first people a new exec will turn to to "read" the org in a large company)
Same for developers. They shouldn't just wait for requirements but also understand their users to some degree.
In the end engineering and product management should develop some competence in the other's area. Otherwise communication is very tedious and error prone.