A common designer makes sense if you assume a few things: the designer was drunk, incompetent, and malign.
"A common designer makes sense if you assume a few things: the designer was drunk, incompetent, and malign."
Even if your accusations had a basis in reality, it would not undermine the fact that design is just as valid of a hypothesis as universal common ancestry.
The character and competence of a designer is an issue for religious and theological debate, not science. We can debate that as well.
When you impugn the benevolence of the Creator you judge yourself. You think you could have done a better job?
What occurs in nature to justify these attacks (especially one upon moral character)?