> ...the brevity of the Agile Manifesto is the root cause of cargo cult agile.
I don't disagree with you, which is why I say that the manifesto is really just actually asking you to exercise your best judgement, given the set of values it proposes. The pragmatic attempts to provide a methodology only give you a list of "thou shalts" that remove the need for people to exercise best judgement in the first place (which is somewhat defeating).
There is some software engineering literature that attempts to provide a theoretical foundation, as I mentioned, but while interesting, I haven't found them terribly useful: people just want a list of commandments to follow.
Is that the manifesto's fault?
Personally, I think the manifesto is probably best used like a diagnostic check-list to understand how screwed up your current work context actually is.