However, I think it's still an interesting topic, and a significant minority can learn something useful.
There should be room for both perspectives here.
I will happily agree with you that there is room for a number of development methodologies.
No it doesn't. It says that Agile proponents who claim it's a silver bullet are talking claptrap. If anything, it says that Agile is a tool and you need to pick the right tool for the job.
Based on the Agile manifesto, the author proposes a scale with "people" at one end and "process" at the other. Ostensibly waterfall is strongly "process" and Agile is a more "people", but he argues that Agile consists of a number of elements that exist at different points along that scale.
He says that the elements down at the "people" end of the spectrum require good, experienced, self-motivated people. If you have these then Agile is more efficient. If you have juniors or average coders (more likely on a large team) then the overhead of a process-based system may work better.
He also identifies the points within the product's development lifecycle where Agile-like approaches work best and when the more hierarchical methods work best.