1. Haifa girl says she’s not sure men were designed to be monogamous. They were – see the first ones in Beraishis! More men are born than women, but by adulthood there are slightly fewer men due to higher fatility rates. Why would more men be born if not for monogamy? Men are meant to learn to control themselves.
Additionally, Haifagirl is not married and probably is very stressed out about the shidduch crisis. I would like to know how a married woman would feel if her husband said “Sweetie, I love you so much. I think I’ll get another wife that I’ll love as much as you. Don’t worry, I have enough love for both of you.” What woman wouldn’t be thrilled at this opportunity?
2. A man who wants polygamy for selfish reasons, is not going to treat either wife properly. Besides for trak (possibly) no one claims they want another wife in order to learn Torah l’shem shamayim – they seem to want it for financial aid, or for their urges – just like Lemech. That’s not impressive. Also, Minhag Yisrael Torah Hi, which is why the above Gedolim haven’t tried to re-instate it.