While I agree overall that Agile is not what it is sold as by many, I am troubled some by the way you presented your argument, but not your argument itself I don't think.
As a CTO/Executive, I read from what you wrote: I have a few unhappy engineers but my project is moving faster and more successful. So I'd say ok, I'll work on managing the edge cases.
As an engineer who's worked in waterfall cycles and almost every iterative cycle you can name, and have designed a few; I think what you meant to highlight was that project managers are claiming work as being more complete then in reality (higher velocity) so they get a pat on the back in the short term but wind up with longer term product problems like maintainability and accountability. Ironically, the two things that engineers like and that help bring job satisfaction.
To that I would agree, there has to be a process that is designed around the cadence of the business and the team. And the process must not be fixed or rigid and grow and change as the team does. This is how you keep people around longer. And PM's are there to facilitate not dictate or take credit away from engineers. But PMs also deserve credit where credit is due and shouldn't be looked upon as the enemy in the engineering cycle, which has always kinda existed but seems to be getting worse at many companies.