An estimated 40% of global websites use Wordpress in some way. It's hard to come up with a more generally applicable set of skills than "Wordpress" at least based on total users worldwide (I'm not here to defend WP, I've never liked it)
That said, I don't think the author's experience with Wordpress has poor transportability into other niches anyway.
That said, I don't think the author's experience with Wordpress has poor transportability into other niches anyway.