In my experience, product people who know what they are doing have a huge impact on the success of a company, product, or service. They also point engineering efforts in the right direction, which in turn also motivate engineers.
I saw good product people leaving completely destroy a team, never seen that happen with a good engineer or individual contributor, no matter how great they were.
I have yet to find a product person that was not involved in the inception of the idea that is actually good (hell, even some founders fail spectacularly here).
Perhaps I'm simply unlucky.
Of course, if the product suite is clueless, nobody is going to miss them, usually it's better the have no dedicated product people, than having clueless product people.