This is a a good question. Let me answer this question in two ways. On the one hand, I generally agree with this statement. Management is central to any organization. Incompetent upper level managers can really hurt a company in many different ways. They can alienate their own work force, make bad deals with other companies, and even be fiscally irresponsible in so many different ways. All of these dangers underline the importance of competent managers. In light of this, I would say that for any organization to thrive, good managers are of utmost importance.
On the other hand, I can imagine some companies that do fairly well even with second rate managers. Part of the reason for this can be because the product or service they sell is extremely popular. If this is so, then the product or service may sell itself. The craze for something can minimize the importance of management at times.
In short, for a company to do well in the long term, management is key.