I can't find Mr Cliff Berg in the list of authors on the official Agile Manifesto website, so I'm (not) sorry to say that Agile is not dead, full stop.

https://agilemanifesto.org/

Just because someone says something is dead, it doesn't mean that's the case.

By this rule, PHP was dead in 1995, and we are almost in 2024, and PHP still rules 79% of all web servers.