So Hacker News and "real programmers" continually underestimate the foundational concept of a CMS. They consider it to be unsexy tech and therefore all problems around it must be solved and boring problems, and therefore they aren't actually aware of what any of those problems are.
The WordPress ecosystem is of course the polar opposite of this, it's populated by billions of dollars worth of businesses that understand intimately what the people operating CMSes and websites in their little niche of that market need, the size of this market is 500 million websites or so.
I'm sure the guy who wrote this article is a smart guy. But he is obviously not smart about the practical uses of a CMS if his worldview is "static HTML sites are better but aren't popular because of evil corporations." You really only need to get paid to build a website once or twice to realize that a static HTML site generator is almost never going to do everything that your customer wants it to do. WordPress realized how vast and varied this market is many years ago and that's why they implemented support for plugins.
You're 100% right comments is like the original use case for having something more like a CMS on the web instead of a static site generator. But there are also a million others.
You just don't get that far with static HTML documents. As soon as you move beyond some minimalist developer's blog you need programmatic logic, and lots of it, to do everything the actual users and customers want you to do. So you use a CMS, whatever CMS fits your needs. And you cache aggressively if you want that site to stand up under a lot of traffic, that's part of the job.
For the life of me, I will never understand why all these devs who think they're so shit-hot want to reinvent the wheel instead of just learn a bit about how caching works, and employ it! Is it another one of those solved problems that's too boring for them?