only curators can force authors to check their texts and improve the quality of publications

Curators and audiences who simply ignore the crap on offer...
Come on, let's keep fighting for it! You (sc team) and I (own stake) are sitting at the source and can keep moving the rudder a tiny little bit in the right direction. That alone will not change the course. But if many join our example, there is still a small chance...

an example [is the] small Ukrainian community

Yes, right. Exactly how it works there was the intention from the beginning. It was: "We will strengthen your community accounts so that you will eventually be able to "look after" yourselves. But instead of pushing this further, the focus was on opening up the communities through SEC. The communities were flooded by "outsiders" who didn't even keep half an eye on the actual community posts. This is the opposite of strengthening a community. This is breeding greedy egocentrics who don't care about community members. And so many play along with this destructive game...

a relatively powerful curator account

This is one reason. The other reason is that you have enough members who are satisfied with this kind of attention.
It is similar "with us" in DU. The community is so small that it has never been enough for great growth of the community account. But that doesn't matter. We are so small that I can oversee this role privately. And I can count on my members: Everyone supports everyone else (as long as they like the article). For most, that's enough; only a few hop from community to community for publications. I'm only talking about publications now, because extending your feed to other users and communities for reading should be a matter of course if you're genuinely interested.