‘My point was that a mechitzah is not required any place women can come, it’s required in “gathering places”. ‘
Not true; it is required for devarim she be kedushah. And as mentioned it is really hard to say that it is more than a d’rabbanan since there wasn’t one in the beit hamikdash until late in Bayit Sheni times, and devarim she be kedushah is itself a d’rabbanan.