This is terrible advice and frankly it's a bit shocking to see so little insight into contemporary CMS architecture and why it exists on a tech site. Yes UGC is a very important driver, but many organisations have an internal community of non-technical publishers and marketers whose needs are served by a CMS.
These original web publishing systems used to have a complete separation of back office and front end. For large publishers back in the day, one of Drupal's major innovations was the concept of a single type of user who could publish using the web front end - that enabled content to be filed and updated from out of the office, covering court cases and music festivals for example. Before they adopted Drupal, I saw a case at a major US publisher where minor changes to a site layout had to have externally conducted pen tests booked in at great cost and then go to a signoff committee which met every 2 weeks - that's what applying strict backend and frontend separation entails.
Publishing to HTML isn't a new idea - it's how CMS's used to work and wasn't up to the task. Using HTML files as a caching layer as you propose is already available in Drupal but has terrible performance due to the number of variants that a modern site can generate (think about permutations of Drupal Views here) and how that hits filesystem limits and OS architecture. You also have the fun of cache invalidation and recompiling every HTML file which uses some upstream fragment you decide to edit - it's ultimately using the filesystem like a very inefficient version of what a relational database is designed for. Quite apart from the latency, that's why people use CDN's instead for caching static content.
Every piece of software we use has periodic bugs which are potentially catastrophic and need patching - yet nobody is saying we should switch to a pen and paper instead of OSX and Windows. I shudder to think what is going on in router firmware and yet somehow we are getting advice that a business shouldn't use a CMS - it's complete nonsense!
If maintenance is too much hassle, the model isn't to switch to static publishing, it's to switch to SaaS - which is exactly what we see. If your needs are too specific for SaaS, then by definition you are going to be creating a tailored solution and managing that in-house or outsourcing.