Relays should be the primary entity in Nostr UX.
Trying to make it all oriented around users / people is a hack workaround.
Discussion
If you want to “follow” someone, you need to go to the same places as them.
This is intuitive and obvious in the real world.
“Where did ___ go? Oh they stopped coming here a month ago. They’re over at ____ now.”
If you get invited to someone’s home (server), that should be a big deal.
You would like to have met nostr:npub14lu6nuqh7v4jazmqw49yzqkmnkw0nletjeuqfdgwqurcp2j9ex5qz37m8m:
But with that said I also think, like nostr:npub1t6jxfqz9hv0lygn9thwndekuahwyxkgvycyscjrtauuw73gd5k7sqvksrw below, that following people directly is an important feature -- even though, as you said yourself, that is just automating the work of going to a relay and asking for posts of such and such. That's kind of the description of the "outbox model", but also I do agree it should be made more explicit in UIs and that ultimately extreme configurability should be an option.
The user should be able to say, for example: "I only want the posts from Bob that he publishes on the astronomy relay, even though he is also publishing stuff to other relays".