One problem with this argument is that users don't agree on what sites deserve that description. If we were to ban the union of all sites that some people feel this way about, that would be a lot of bannage. I don't think HN would be better for this.

The main thing to understand about HN is that we're trying to optimize for intellectual curiosity: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor.... I'm not saying that other things aren't valuable, such as the considerations you're raising—they are. But we can't optimize for one thing without foregoing other good things.

We do ban and penalize some sites on HN. We ban the ones that are clearly off topic or spam, and penalize ones that are quite likely to be off topic, or whose popularity/interestingness ratio is too high (which is basically almost all major media sites). But even when a site is banned, when a particularly good article appears there, users can vouch for it and upvote it. All of this follows from what we're trying to optimize for.