Veganism

[Fake Messiah]

To put it another way, why should we prefer your analogy over the analogy of somebody who is initially a very bad shot when it comes to shooting an arrow at a target, but with lots of practice becomes a better shot, despite perhaps still being a bad shot, and hits the target more often due to improved skill rather than just lucky shots (so there is more agreement later on, moral progress)?

It is a false analogy. In your archery analogy, the target exists in physical space. Both the archer and the spectators can see it, touch it, and agree on where the bullseye is located. In morality, there is no "visible" target. Unlike a physical object, we cannot point to a "Moral Fact" in the natural world.

When an archer misses, they know they missed because the arrow is in the dirt. When societies disagree on morality (e.g., the ethics of euthanasia or wealth distribution), there is often no consensus on who "missed" and who "hit."

If morality were as objective as target practice, we would expect to see a convergence of belief over time as "skill" increases. So, moral "progress" is actually just moral change—a shift in cultural sensibilities rather than a closer approximation of a pre-existing truth.