Yes, I agree, there should be a "single person who is responsible for ensuring that the product should delight the user". But that person is the product leader,

Yes, I agree, there should be a "single person who is responsible for ensuring that the product should delight the user". But that person is the product leader, a single GM or whatever you want to call it, and the task should not be delegated to a team of PMs. Someone needs to oversee designers, user experience researchers, business analysts, developers, operation engineers, testers, etc. Thats the role of the person in charge and thats why they get paid so much. This person should also be accountable for "the product delights customers" piece, and if this doesn't happen, is also the person who gets replaced.