Isn't that at the core of Steemit's philosophy?

That's exactly how it is!
The two criteria you mentioned are actually not that difficult to recognize - whether you like the content or not.
But we've long agreed that “He's my best friend” or “This user is good because he's always good, so he'll be good now too and will get his vote because he always gets one” are not quality criteria.
Haha, we've discussed this so often, I really don't want to open that can of worms right now. I think it misses the point anyway.

I have a certain circle of authors whose content I like and I'm more likely to vote for them than for an author I don't know.

Yes, that is human. And I don't think there's anything wrong with acting as a private user (I haven't cared about the “jerk circle accusations” for a long time). However, if you're dealing with a bunch of other people's SP, this approach to voting can have a very delicate flavor. You and I know enough examples, the gorilla probably knows even more... In this respect, I also think it's very right that the curators change more frequently. Of course I know that this means more effort (not only technically, but also in terms of building trust), but in my opinion three months should be the maximum. Perfect: rolling, so that one member always remains to briefly train the new ones, who then take over this part the next month.
Phew, another topic with a long beard...

there is no old Steemit anymore, and there won't be

Richtig! Fun fact: In the meanwhile the "New Steem" exists longer than the "Old Steem" actually did. It's time for all the stubborn people to understand that... ;-)