Good, get him the fuck away from Wordpress. Though frankly, a better solution might be for businesses to ask themselves whether or not they need Wordpress anymore.
In the mean time, if you're unable to derisk Mullenweg out of your business stack, this is a good first step.
The uptick in Webflow usage alone would suggest the damage has already been done.
WordPress dominance of the web has certainly peaked, but history indicates there will be several years in which to continue to extract comfortable profits while riding it down. e.g. Oracle, a database that almost no business has actually needed in decades.