It's an SPA written in react, so unsurprisingly it requires javascript. Preloaders being harmful is purely your opinion, and your example of why they're harmful doesn't seem convincing to me.
I can see a case for a static version of the site being available, and I think with a bit more work they could have generated one from the react source.
That said, and this is more of a generalization, I think hacker news has a bias towards JS-free sites. Accessibility is an issue, but you can have a fully accessible JS-based site. JS can make it difficult for a scraper to interact with a site, but a separate xml (or whatever) document would be better to allow scraping anyway.
Basically, when developing a site at some point you decide how much effort you're going to put into supporting users who don't have javascript (usually out of choice), and for most people the answer is zero.