A problem with classifying world views as polytheistic or monotheistic or atheistic is that we're not always using the word theos, that is, god, in the same way. Monotheistic worldviews that emphasise the oneness of God have rarely excluded concurrent belief in angels. Which begs the question: how exactly do we differentiate angels in monotheism from gods in polytheism?
In my experience the difference between polytheistic gods and monotheistic angels is less stark than we've made it. In fact I am inclined to suggest their equivalence and assert what monotheists call God is more akin to what polytheists have at times referred to as the unknowable god or formative chaos or ultimate reality from which all gods emerged.
This ambiguity besets dialogue between monotheists and atheists also. For not only are atheists mistakenly inclined to draw an equivalence between the God of monotheists and the gods of polytheists, but I have met many who identified as atheist whilst still holding to belief in angels without seeing any problem with that self identification.