Let’s not make rash assumptions. All you just said is based on your unsupported assumptions. Aside from no one even being close to his stature in his generation, the facts are none of the Gedolim opposed him. The overwhelming effort he referred to was regarding the hamon hoam.
The Baal Shem Tov took no position on this matter.
And many Sefardim, Yemenites, and other fine fully Torah observant Yidden have had multiple wives as recently as even after the State of Israel was founded after WWII, when they brought their multiple wives from their home countries to Eretz Yisroel.