I have been a PM for most of my career. Lose engineering and you have no ongoing product, sales and you can not sell it, support and you can not service it. You get the picture. PM is not required for the basic operations of the business. Great PM is fundamental to success, but not to the day-to-day management of the business.

There are such things as "one developer shops".

There are no "one PM shops".

Case closed.

As an engineer I really appreciate the work of good PMs.

There are 2 specialized positions (not roles) that I have been able to eliminate in a couple of successful projects (in a startup). These are Product Management and Quality Assurance. I think both the tasks are important enough to be entrusted to engineers, rather than getting someone else do it.

There are advantages to getting someone else to do some of your work half as good, for example they can offload work for many people at the same time. It's good for morale and concentration.

How did that work for you? Were the engineers assessing the overall market and competitive landscape and training the rest of the organization how to position and sell the product? Please tell us more about the project and how it went.

It's harsh but it's quite true. Engineers (and other people!) would otherwise have to devote time and effort towards product goals and timeline management -- it would likely be only half as good as a full-time PM but they'd get it done without trouble.

Product managers are an extension of people's normal employee workflows but expanded for coordination and communication, however there's nothing preventing the PM from exercising minimal responsibility on things like product design and whatnot.