I wouldn't necessarily say OpenAPI and Composer are new technologies, they're tried and tested and commonplace across most PHP projects. I totally get his point. He's an older dev who's sat comfortably for too long with an ageing stack, and now is completely behind the new guys who are coming in from other companies and wanting to change things.
I think the place we disagree is that I believe technology is a place where progression is a hard requirement of the job. Computers get better, customers get more demanding, old solutions improved. You need to improve, every day.
My issue is more when the response to a new piece of minor technology that will make our lives easily is: "I don't want to learn YAML".