Simchat bat, I believe, was invented (or at least applied by those who don’t really have that minhag) for the wrong reasons.”
I have always subscribed to the belief that “metoch shelo lishma, ba lishma.” Perhaps SOME Jews do certain things for the wrong reasons. That does not mean the things they are doing are inherently bad, only that the motivation behind them MIGHT be. So you take those same actiona and imbue them with a sense of kedusha and hakoras hatov to the Aibishter, and it no longer has the taste of reform or reconstructionist, but becomes something that belongs to us as frum yidden.
Just because some minhag arises from a less frum source, does not mean that minhag is TREIF as has been said flat out here. Frei Jews also become spiritually inspired at times, and some of their ideas have merit, even if most do not. It is all in how we handle the idea and bring it to fruition that determines its worth. I think that making an oneg shabbos on the Friday night after the birth of a baby girl, is a lovely way to say brucha habaa. I wish I had thought of it when I had my babies. And though the boys may be having a bris, the girls are the bearers and rearers of the next generation of Yidden.