He asserts that Agile itself is corrupted, and we should reject the word and all its related practices, education, literature, trade groups, and conferences.
But he's wrong.
These terms (Eco, Natural, and Agile) aren't an excuse to turn off your brain. You still have to know what Agile (or Eco or Natural) means in order to evaluate that claim. Expecting everyone who uses a term to use it in exactly the same way is ridiculous. Changing it from Agile to "agility" won't make any difference or distinction. The same shady consultants and book writers that create "Doing Agile Right" books and courses will just write "Programming with Agility the Right Way." The same companies that say "we are agile" while writing four-page user stories won't wake up and say, "oh, our practices don't exhibit agility", they'll continue to say it just the same. And you'll still have to evaluate their claims, just the same.
But he's not just wrong, he's harmful.
Dave suggests that agile conferences, trainings, and apparently all literature on the subject is counter to the original spirit of the manifesto. Maybe is is, I wasn't there so I wouldn't know. But I know that they wrote about teams coming together regularly to tune and adjust their behavior. If your conference doesn't feel like that, it's a bad conference. If your training doesn't feel like someone sharing their experiences so that you can use what works, it's a bad training. If you're ignoring that principle by requiring that your teams "do Scrum by the book", then changing from nouns to adjectives in titles and slides isn't going to fix that.
Rejecting the experiences of others isn't going to make you better at doing agile, being agile, or performing with agility. His advice to "just do these four things, and build up your experience" while an accurate general guide (that I like), it ignores the fact that he has, himself, taken at least fifteen years to get to this point. Should we all just derive the fundamental principles of calculus ourselves as well? Or would it be better to talk together, as a team or as an industry, about what works and what doesn't?
He talks about "protecting" the word agile -- there is no practical way to do that, unless you want to trademark the term and sue those who use it in a way that you don't approve of. But I get the sense that Dave isn't a big fan of the Scrum Alliance either.
So what do we do? We keep being leaders, we keep sharing what works, we keep pointing out when the emperor or alliance has no clothes. What we don't do is mess around with meaningless semantics, and in the process reject an entire community and network who, on the whole, has changed the industry for the better and continues to push the envelope.