So as far as I can tell, what you're saying is that it's impossible to take any process ideas from an external source, because every team is already maximally efficient.
Nope. I'm saying that the process of programming is what we should focus on getting better at. We should take improvements from wherever we can find them. Getting better at the process of Agile or Waterfall or Scrum or XP or Kanban or whatever else is dreamed up is tangential to our progress as programmers.
I agree that nobody should focus solely on getting better at, say, Agile. I also agree we should work hard at getting better at programming.
However, I don't think that focusing on programming alone is sufficient. A lot of projects fail for reasons other than bad coding, and almost no project exists where programming is the end purpose. You can do all kinds of great programming, but if you make the wrong thing, you're screwed. Ditto if you have a bunch of individuals doing great programming that doesn't add up to a functioning project.
I also think you're creating a bit of a false dichotomy. When I first tried XP, it wasn't for the sake of doing XP. It was because I wanted to improve how we made things for our users. So exploring XP wasn't tangential to better programming; for me it was closely related, in that programming was a big part of making.
Nope. I'm saying that the process of programming is what we should focus on getting better at. We should take improvements from wherever we can find them. Getting better at the process of Agile or Waterfall or Scrum or XP or Kanban or whatever else is dreamed up is tangential to our progress as programmers.