I don't really think you have said anything different than I have to be honest.
One thing that I take issue with is because someone works for a company a long time, that alone shouldn't be regarded as 'making a significant commitment'. In my years of career development, that was regarded as someone who lacked ambition and was frowned upon. Also I may add, that its not the years with a company that's important, its the contribution that person has made which is.
IMHO To make a good company, you need employees that are willing to put the effort in to make it good. Employing the right ones in the first place is the key (and very difficult)
'Promotion to incompetence' is a term I have heard many times and supports what I have said. If they are incompetent to manage, but have still been promoted, then they must have achieved what I said in my first post which is they are very good at interacting with the people who matter for their career development. Management skills don't always come into it.
As a manager, I have good days and bad days like everyone else but I make a point of going out of my way to put something right that I have gotten wrong. I am a tough person to work for but those that do, tell me they wouldn't want it any other way