> Gottfried Leibniz suffered no small amount of flak for his conclusion that the reason the world looks the way it does is because it's already "the best of all possible worlds": you may think you see an improvement, but you lack divine understanding and therefore you don't see how it would actually make things worse.

Isn't this line of thought disproven by a single improvement? People before the improvement could have argued along the same lines and then be proven wrong.