At the risk of getting in trouble again:
The Torah actually permits polygyny, for Jews and non-Jews. However, this isn't like the mormon doctrine, which is connected with producing "gxds" to live in other worlds. It's simply permitted for a man to have more than one wife (a wife can have only one husband). A husband, however, would have to have the means to properly care for and support each wife. It's never been something most people could handle. Monogamy has been the practice for millenia now.
However, back in the Middle Ages Rabbi Gershom issued an edict banning polygyny for 'Ashkenazim. I have heard that this edict has expired, and I have heard that it has not. What do I know? And while it was still permitted by Mizrachi (Eastern) authorities (who lived in the Arab/islamic world), on the founding of Israel the rabbis there ruled that all Israeli Jews should practice monogamy.
Outside Israel Jews have been bound since Talmudic times by the dictum Dina' deMalkhuta' dina' (the law of the land is the law).
They should change the law in Israel, then. It has decreed, but must still be nullified. Rabeinu Gershom made the decree for everyone, but his influence did not extend to the Mizrahi communities, who never excepted it.
Myself, I am entirely content to remain married to only one woman, having lived that way for nearly 30 years, and being unable to afford more. It’s the young men that concern me, who are often forced to make huge concessions to get out of a bad marriage when they are not at fault, because otherwise they cannot marry again. I’m also concerned about demographics. A man who can afford more than one wife, and whose first wife is agreeable to it, ought to, for the sake of the nation. Arabs and Bedouins are not similarly constrained, and at this time the rationale of Rabeinu Gershom’s decree no longer exists.