I am seeing a parallel to modern day socialists/communists. Despite hundreds of instances of real adherents to the philosophy really trying in earnest to achieve communism in a wide variety of cultures, geographies and situations, it never works. We know why it works and economists can tell you exactly why it doesn't work. Yet, every new case of communism's failure is chalked up to not being "real communism" or being "bastardized by dictators".
> economists can tell you exactly why it doesn't work
Can they now? It seems to me that the more "exact" an economist gets, the more they should be ignored. Economics is a fiendishly difficult discipline and anyone who claims exactitude should be setting off your B.S. meter.
There are parallels to Christianity or Islam too: if you don't 100% own the brand, it will be coopted by people who will redefine it and confuse everyone. Only the Catholic Church really controls its own brand and can actually define what it even is.
The big difference to communism is that the Agile Manifesto was written from personal experience of having working teams. The Communist Manifesto was wild speculation about how society could maybe work.
I have worked following the Agile Manifesto for soon 13 years and it works very well. No surprise really, as it's just treating everyone like adults.