A perfect example of how haskalah has infiltrated the discourse of otherwise frum people.
Academics say that the cherem was because goyim had forbade it. Rabbeinu Gershom makes no mention of that. He says it’s because people can’t do it for the right reasons. It’s detrimental to bnos yisroel.
Needless to say, i don’t believe you’ll find even a handful of girls who would consider being a second wife. Even the chazakah of tav lemaysav tan du, that women would rather be with basically anyone than be alone – is “tan du”!!!! A pair. Three or four is not a pair.