I think this is one of the most realistic responses here.

I think it's in most party's self-interest to keep playing the "agile panacea" game.

1. Salesman sells something that doesn't exist, pats self on back

2. Engineers asked to build integration/features on arbitrary timeline

3. Doesn't happen, everybody unhappy

4. Scapegoat needed. Says we didn't agile right. Project Manager hired / Deck of Fibonacci cards bought.

5. Go back to 1