We can examine the idea that such a hypothetical designer is both competent and benign.
This from 2008
You have posited in this thread the idea that maybe some entity might be making mutations to direct the direction of evolution.
Pretty much the "noodly appendages" of the FSM but in mutations rather than isotope ratios.
That is indeed not testable, but we do know that when organisms are adapted to their environment, there would be a greater number of occurrences of detrimental mutations than beneficial mutations. Indeed, we see this in our own species with children who suffer from genetic diseases.
So we have to posit a designer with the ability to direct mutations who is happy allowing suffering due to harmful mutations, and by their very nature these first appear before the victim is sentient.
Now one might argue that it's okay because original sin* means that they have inherited sin from somewhere or that the creator can do whatever it wishes with its creation. However that's a moral code which is happy with slavery (which, of course the Bible was). Just because someone creates a sentient being, one doesn't have any ownership of it - that would include any hypothetical future sentient robots. And yes I can judge any hypothetical designer by my moral standards.
anyway this point is made in this post in the "what is Marvel's dumbest character thread.
The highlighted
*Only exists if you believe that Genesis is actually true.