In the Mitzva of Hakhel, we are told to gather all of Klal Yisrael during Sukkos of the year that follows Shemittah to hear the reading of a large part of Sefer Devarim. The Torah specifies that men and women and converts and children attend. הקהל את העם האנשים והנשים והטף וגרך אשר בשעריך למען ישמעו ולמען ילמדו ויראו את יהוה אלהיכם ושמרו לעשות את כל דברי התורה הזאת The purpose of the gathering is so that all that attend will hear and learn and so that they will fear Hashem and do His mitzvos.
I'm not going to discuss the issue of women learning Gemara, but it's obvious that the women had to be there to hear the Torah, both at Hakhel and at Mattan Torah. The raya that they were essential to Kabbalas Hatorah is that the three day delay was in order that the women should be in a state of ritual purity, such that they would be receptive to hearing the words of Torah.
It's obvious that Chazal were not sanguine about women learning Gemara in the same way as men. Witness Rav Nachman's statement in Megillah 14b regarding Chulda and Devorah, and, of course, Rebbi Eliezer's words in Sotah 20a. Both can be interpreted differently. I know that. If you're not seeing the subtext of those Chazals, then we're not sharing a lexicon and we're not really having a conversation. Also, if you think that Chazal did disapprove of women learning Gemara, but they were not enlightened, you're not the kind of person I'm interested in communicating with. I don't need an audience of or a conversation with kofrim b'divrei Chazal and azei panim.
Finally, it's also obvious that the times, they are a-changin'. The current Yoatzot and Rabbaniot have worked hard to attain what they've achieved, and while no doubt equal to their cohort, they are not worthy of comparison to the poskim that learned in traditional yeshivos. But there will come a time when some gifted woman will publish halachic opinions that stand up to criticism and which will be shown to be of a caliber equal or superior to accepted male poskim. The Yeshiva world will never accept this: we have plenty of examples of geonim in Torah and Yir'ah who were rejected by the right wing because of some theological or political flaw. But this will not matter to the Modern wing of Orthodoxy. On the contrary, they will celebrate and embrace this phenomenon. At that point, Modern Orthodox Judaism will experience an irreversible change of trajectory.
This beginning of this sea change is all around us, and the movement is inexorable. Most of us know a woman who is learning the daf, or giving a shiur on Gemara, or writing articles on Halacha. The extent and degree of this phenomenon is totally unprecedented. For all I know, it will lead to improvement. I can't say that men have done such an excellent job, but certainly the female perspective will not be the same. As I said before, Chazal's words are not encouraging.
Whose fault is it? Rebbetzin Sarah Schenirer and Rabbi Nosson Scherman, that's whose fault it is, Beis Yaakov and Artscroll. It's not really a "fault." What they did was no different than what Rabbeinu Hakadosh did, and it saved tens of thousands of Jews for Yiddishkeit. But there are unintended consequences, and this is a big one, and it's gonna shake your windows and rattle your walls.
From the comments, it has become clear to me that I need to explain what I perceive to be the problem. To me, the biggest problem is the feminization of Torah. Torah, as it exists now, is the product of a male approach. We learn by arguing, we fight each other over every word, and we build complex structures that define our view of Torah as a gestalt. I believe that a woman's perspective would be very different, and that after a few generations, the Torah that stems from a gender neutral learning would be unrecognizable to us. This would have two terrible results: The Chareidi world (such as Lakewood, Telz, Mir, and their offshoots) would utterly reject the legitimacy of those groups that exhibit these characteristics, to the extent of refusing to join them on rabbinical action committees; and, concomitantly, this would generate an unbridgeable gap that would start out based on theological differences but would ultimately express itself in enormous halachic differences and would be as wide as today exists between the Orthodox and the Conservative.
The immediate response of the modern crowd is, "do you have any empirical data that support your assertion." No, I don't. So consider yourself to have won this argument, and have a good day.