Yes, monotheism is relatively new to the table and has been very successful for a couple of thousand years. Calling it a parasite explains absolutely nothing.
Depends on exactly what you define as monotheism, actually. From all the evidence we have, including literally thousands of written prayers from the Sumerians, everyone believing in exactly one god as the real thing was actually the
overwhelming majority situation.
At it even makes sense too, if you think about it: Gods
* are a father figure. Nobody fancies themselves being the *ahem* son of a thousand fathers
Polytheism is actually the one that appears later, by the time you start dealing with ruling or allying with several cities, each worshiping a different god. Like, you have the city of Eridu which worships Enki, and Lagash which worships Ninurta, and Uruk which worshipped Nanna aka Sin, and Uruk which worships Inanna. (Actual cities and actual gods of those cities, btw.) And none of them is going to go "well, we were wrong to worship Inanna, we should worship Sin instead, if our new overlord worships Sin." So you invent whole pantheons where Inanna is actually the daughter of Sin, and Sin is subordinate to some other guy, and so on, so everyone can play along.
What's newer is
exclusive monotheism. I.e., being the kind of assh... err... hat (don't want to trigger the mods about that again

) who'll go, "no, all your gods are false, you all are mistaken, only our Yahweh is the real deal."
In a sense it's actually a step back.
* But it should also be mentioned that that only works about Gods or at least great ruler spirits. If it's animism where everything is a spirit or has a spirit, you can still have thousands of smaller spirits around naturally.