Author here. I think in general this is sound advice, but in Emacs it is an incredibly convenient utility. I use them all the time. Mostly simple things like wrapping function definitions, or even other macros that wrap function definitions. Most of my lisp experience is in Emacs where the config layer is essentially exposed through an elisp API. In that context, I find myself using macros a lot. But if I was building some software from scratch, like say a data processing system, I can't immediately think of scenarios where I would define macros.

Worth mentioning in Elisp that even if you don't define your own macros, you use them more often than you would think. defun, unless, def-custom, etc (more examples in the blog post) are all macros. The fact they look and feel like non-macros like special forms and built in functions implemented in C is part of what makes elisp so cool to me. There are plenty of homoiconic languages, but you rarely feel the distinction between program and data in elisp, and macro-supporting lisps in general.

Why?

Meh, that seems to be a bit of a clojure thing. In the Racket world, with hygienic macros and phase separation, they'll routinely write macros returning macros, etc.