Are you reading from a mobile device perchance? I expect it would look fine on one.

But I can assure you, it does not look fine on the desktop. I have literally one header and a four sentence paragraph on my screen right now.

No, a desktop (well, laptop) hooked to a 24" UHD screen.

It shows a header and ~3 paragraphs.

If you want a "reasonable amount of letters/words fits on each row", then make the column smaller. Don't compare this to print - no even semi-mainstream printed publication or book has type this large.

On desktop, the type on this site is unreasonably large. It is considerably larger than any other website that has long form content. It is extremely uncomfortable to read on my 13" MacBook Pro (which is a fairly common laptop/screen size).

Thankfully Safari gives me a 'Reader' version that's much easier to read. Compare the Reader version https://imgur.com/a/gs00JWD to the original version https://imgur.com/a/Waob1VZ

The font size for the body text on that site is 40px on my monitor and 35px on the laptop screen. That would be large for top-level headers. 16-18px Arial is just about the perfect size for primary text on any screen. It was a little excessive on 800x600 CRTs in the '90s, but not by much.

There are some nicer fonts than Arial/Helvetica out there, and I'd say the author used one of them here. The text looks really good at 18-20px, which is about the same size as 16-18px Arial.

I can't understand how so many "experts" are constantly screwing this up so badly. Some of the worst offenders are web design and typography bloggers.

Right, but you also have to mindful of how many rows are on a single page (or, in the case of the web, in the viewport). When I have to scroll after every paragraph, I find it a) harder to pay attention b) more strenuous on my eyes.

That being said, it's fine at about 50%, and so far, the content is really interesting!