A huge problem with agile is that managers often say they’re using agile, when in fact they’re just allowing completely undisciplined development and calling it agile, without doing any of the actual methods used in real Agile-with-a-capital-A development.
So rather than reaping the benefits of Agile, you just gain undisciplined development and unpredictable, ill-prepared product releases.
And yeah, there are areas where Agile should not even be attempted, IMHO, never mind fake agile.