binding hera does not seem to turn off all the things she is in charge of closer to resisting gravity than anything else.
This is a really hard sentence to follow. But, no, binding Hera doesn't "turn off" marriage or remove all women from the world. Just like killing Poseidon doesn't remove the Oceans. Remember, The Greek Olympian Gods inherited their domains, specifically Zeus and his brothers drew lots for who would rule what.
If your vision of the gods includes "when they are dead or bound, the thing they represent is removed from existence" then you are going to have a hard time finding ANY "gods" in mythology, because that doesn't happen in myths. And many many myths involve various gods being bound or killed at some point.
Also, most of those are gods doing it to each other, which is a more open area than humans stop caring, so now there are no gods.
Not all of the examples I listed were god on god. Diomedes was just a normal man. Growing old and dying of old age has nothing to do with god on god. Also, in many myths you have to contend with other beings like Titans, Giants, monsters, ect which were threats to the gods.
And I don't think the idea of the gods needing something vital from humans is a matter of "they stop caring". It never seems to be about Apathy, to me.
it is fair to make gods vulnerable but gods fading with out worship feels like a left over from when lots of people had the magical die-off from their setting at some point.
Maybe that happened for some people, where they wanted a magical die-off, so they made this connection. But I think it persists for deeper reasons.
There is always a question about "why worship?" Take characters from comics, like Superman or Green Lantern or Flash ect ect ect, they are powerful enough to be gods and have defeated gods in the past. Yet, they never seek out worship. In fact, the very idea of worshiping Superman makes no sense. And it isn't because "well, he isn't a god" because, again, he has fought and defeated beings who ARE gods. There isn't a meaningful distinction.
So, why do Gods seek worship? Why do they encourage and reward worship? You end up with one of two avenues. 1) The gods are egotists who want people to worship them 2) They get something from the worship of mortals. Something important. And it has to be worship, not the same as just "you need to work for me" and taking the role of a king.
#1 is terrible. It paints every single divine being as horrible. So, a lot of us go to #2. There is something they get, some vital essence, that is needed for the Gods to be Gods.