Thus begins John Mecke’s essay Agile is Dead (So is COBOL, XP, RAD, UML, SAFe, etc). It’s an enjoyable, step by step takedown of the {whatever} Is Dead new paradigm promotion treadmill.

The key takeaway … is that you should experiment to see what works in your environment.  Every company is in a unique place at any point in time.  Your market position, your level of resources, your ability to execute are all specific to your situation.  As Dave Thomas says no rules are universal.  What works for Google may not work for you.  

You should not abandon things that have worked in the past in favor of some shiny new toy just because they’re old.  Edgar Codd’s approach to database normalization works just as well in 2021 as it did in 1972.  UML state machine diagrams are still an efficient way of documenting complex designs.  Spring planning, daily standups, and retrospectives are still very effective ways to build software. You should synthesize what has worked in your environment with new ideas.

Legacy == Proven