We have no good evidence we were even visited in the first place.. we also have plenty of good explainations how organic life first emerged and we observed parts of these phenomena..certain proteins forming and such in tide pools too..
Even if: coming back to teach up your creation to perfection may be a very human concept.. aliens may have seeded this world accidentally… it is like us forgetting this yoghurt package in your room. You come back eventually boom life is there… it is much more likely aliens would seed life accidentally than plan it out.