I don't know. Still, at a time like this I would expect a 99% static public website to be up, running and serving all comers. This is a complete mission fail, both in terms of using PHP and in terms of not having a fall-back plan in place.
[EDIT: I see I may have erroneously extended your criticism to sites other than NCSC, for which it does make sense. I would still defend using PHP.]
Now are there more powerful tools out there that result in more scalable websites? Sure. My personal sites are built around static site generators for that exact reason. But none of better tools are as easy to understand for non-programmers as wordpress or one of the other click-and-drag CMS tools.
That you want your content to be readable from everyone doesn’t mean you want the admin interface to be available globally.