I would consider the eradication of smallpox and such things as pretty good evidence that we can do it better, just as its existence seems like pretty good evidence that the world we're in was not created by a god, but a motivated theist could come up with a host of other possibilities.
We cannot, after all, run a control on the history of the world. We can make up a million possible stories in which, for reasons we needn't elaborate, the world would ultimately be better off if we hadn't gotten rid of smallpox in the way we did. Or, as some people have suggested, it could be a bone thrown to the human race to make them feel good, and all part of the plan.
The arguments for doing it better tend to be anthropocentric, which is in accord with the way the human authors of the Bible spun the story too. Sure, if we were in charge we could make a universe that's better for us, but if the universe was created by a god, he's the god of it all, the small things too. There's a special providence in the fall of a sparrow, so we're told, and the smallpox virus is a part of creation too.
He is rather wasteful, all the universe created just so humans can exist. If you took the volume of where we can inhabit as a percentage of the volume of the universe, we're as close to zero as to make no difference!