And PMs can talk to customers but don't, because it's better for their career to align with the executives and implement their amazing ideas

Which isn't my experience at all. I've always seen PMs spend a bunch of time on the road talking to customers and in executive briefing centers. (And I was one in hardware at some distant point.) Engineers, sensibly, don't really want to spend that much time with customers--and even if they talk to one or two it sort of colors their opinions by that one customer's requirements.