To be perfectly honest, I had a friend, the one who originally introduced me to Reborn, who raised some of the same criticisms as you. He wasn't used to having to train a full team from the get-go, and never got past Corey because of it. And, yeah, I can say one thing confidently: Reborn isn't for everyone. Different people play Pokemon different ways.
Also, I think the fetch quest speaks more to Victoria and Kiki's characters than bad writing; they must stick to tradition. After all, what's waiting a few extra minutes for a quick battle or badge test? It is the tradition, after all. And these small diversions add up until you're... traversing the Bysbyxion Wasteland because there's no other way to contact Aya.