"Product designers" are also made fun of by the people doing the actual work. I agree that it can be difficult, but those difficult decisions are worked through by the people with their hands and eyes on the actual thing (or on the actual code), not by the "idea people" who spout off nonsense and expect their fever dreams to magically turn into a useable product or useable software by their little minions beneath them. No, their little minions are the only ones who actually know how to do anything, and the "product designer" is just in their way.

A "product designer" is someone who got daddy to fund their "gentleman's Cs" MBA degree and then posts online saying they have a brilliant idea for a company and they just need to find some programmer to implement their grand "Facebook for Dogs" idea and they'll graciously give them 20%. Someone who idolizes Steve Jobs and whose eyes glaze over when any of the actual fractal complexity of the world is presented to them.

I'm making a game right now, and I'd kill for a good game designer.

The gap between "high level goal" and "features to implement" is just as complex and squirrelly as the gap between "features to implement" and "lines of code".

I work on a project with a decent ratio of engineers:designers. A good designer is not just "ideas people", they are fairly technical without getting into the nitty gritty.

If one side gets too much power then it can land in situations like you describe (design makes unrealistic requests, or engineering over constraints the product). When the balance is right then working becomes quite amazing, nothing better than seeing my work (engineering) used to make stuff I couldn't even think of and I can see the appreciation of helping design make their vision come true.