I've spent some time interacting with product managers as an engineering manager, or head of a functional area. I've also been "acting" PM for an internal product at a medium size tech company. I think product management entails some of the most important things a company does. But it's really hard work, and many less capable PMs gravitate away from it and more towards either "driving" (i.e. micromanaging) the engine…
I don't believe in Product Managers or Project Owners as a net good towards building a better product or a better company. The most successful teams I have been in had no dedicated product role, instead, all decisions were made by the developers. My current view is best to remove all type of non technical people or even mildly technical people from the developers' way and let them build in peace.
PM for retail company did long stints in merchandising at Costco
PM for spreadsheet company was a former banking analyst
Most companies hire under qualified generalist PMs who have to learn everything about their market from scratch; it’s very challenging and prone to outright failure.
Hire fewer PMs, and make sure they bring a key skill to the table. Let Microsoft and Google train the juniors.