The problem with monotheism is that - if it were approached honestly - you'd need to not only establish that gods in general can exist, but you'd need to establish that the number of gods is somehow limited to one.The problem with polytheism is that if there are multiple Gods then surely they must have something or someone that created them ?
Justifying monotheism has all the problems inherent in justifying polytheism and all the problems inherent in justifying hard atheism, only with a bunch of problems of its own.