That's why they are starting only with verified sites. To combat the spam feature. But of course, they are creating a closed system with that. Which also is not the best

Easy fix.

Make blocking a poster block posts containing their articles, too. It makes avoiding nonsense easier, not harder. Then streamline the ability to share and collaborate on collaborate on curation (both "read this" and blacklists) and leave the power in the hands of the users. Once the tooling works, you could, as a host, suggest "recommended blacklists" or "recommended curators" for new users.

The bonus of this is that you can still moderate and ban clear "over the line" stuff (whatever your standards are), but stuff that's more controversial doesn't have to have users exactly match their instance, and they aren't forced to migrate if their/their instances stances change. (That doesn't mean don't actually ban racism or malware or spam bots. You could use the same list tool to ban all that without doing it personally every time. But people who think you should ban more stuff that they don't like would have alternate ways to handle it.)