I think I've finally got it figured out, but I don't know if I can explain it in a way that doesn't make me sound like an idiot.

According to Sonny Joon and his grandfather, the Teachers left all these artifacts here for us to find, along with the obscure set of instructions they gave to the Annunaki. When the artifacts were assembled, they became a beacon, which is what Jin calls it in his notebook. When the Teachers see that light, they know we've solved the problem they left us and are now ready for the next step in our evolution.

Wouldn't it be lovely if we had someone else helping us out like that, instead of just stumbling along on our own? I can see the appeal of the Annunaki, where there's some large conference of wise beings helping us grow towards wisdom ourselves. Shame it's fiction.