* Scrum is not a methodology or a process, just a framework
* There is no product manager role in Scrum, but there is a Product Owner role
* There is a big difference between "ownership" and "management", which could be the source of some of the dysfunction you are seeing
* There is no formula for a Product Owner to follow. Remember, Scrum is just a framework, and the Scrum Team gets out of it what it puts into it.
* You make the POs sound like victims by saying "... have not been able to really do anything about it". I think they were the wrong person for the job.
* Product Owners should not attend the daily Scrum. It's just for the development team. Instead they could spend this time innovating!
* A product's vision is manifested in a properly refined backlog.
* It sounds like the first two struggles you listed (MVP and complaining customers) were caused by the PO being ineffective. The next three are just aspects of a PO's job responsibilities
* Effective POs should be focusing on competitive research, market assessment, positioning, go-to-market readiness, etc.
* I'm not sure where you came up with the notion that POs should be heads down. The Scrum Guide describes just the opposite.
I do agree with your antidote at the end, that a PO should start with the goal, be transparent, and trust the dev team. If your article just these points, readers might find it valuable.
I know you want to sell your product, but if you are going to bash Scrum in the process, you might want to up your game, and your facts.
Richard