I don't think moral progress necessarily implies an objective morality. We can't be working towards something we can't know about. We just happen to be walking

I don't think moral progress necessarily implies an objective morality. We can't be working towards something we can't know about. We just happen to be walking towards it, or not. What we feel to be moral progress isn't a statement about our discovering an objective morality but rather a social consensus based on, as you say, greater knowledge and altered perspective. Moral progress is the idea of an expansion of collective understanding and acceptance of moral beliefs/axioms.