Devs (like yourself) might generate scaffolding for a greenfield project very quickly and be amazed and claim they're more productive, but I don't think that is evidence that an experienced developer will actually be more productive.

Honestly, project scaffolding is such a small part of the job. I spend a lot more time reading, designing, thinking critically about, reviewing changes to, and generally maintaining code than I do creating greenfield projects or writing boilerplate. For all of these tasks having actually written the code myself gives me an advantage. I don't believe today's tools are a net positive.