And usually:

C: Therefore you’re doing it wrong.

And once an “agile guru” enters the conversation:

D: You need my book / seminar / services.

Is agile the socialism of software development methodologies?

(Not for any deeper reason, only that whenever socialism fails, people tell you that 'real socialism' hasn't been tried, yet.)

It's the same with every *-ism.

That's not actually true. To give a silly example: does anyone (seriously) claim that 'true fascism' has never been tried?

Or: liberal democracy (I'm sure you can find a synonym that ends in *-ism) has been tried. It's been doing ok-ish. Obviously it has warts and all. But more importantly: approximately no one ever seriously claims that 'real liberal democracy' hasn't been tried.

Similar for constitutional monarchy, or 'social market economy', or dictatorships, etc. People can mostly agree that the real deal has been tried.