I think the different perspectives here have a lot to do with how each side views limud hatorah. The more yeshivish end of the spectrum, those like shlishi that staunchly oppose women learning Torah sh’bal peh maintain a view that the point of limud haTorah is simply to learn. There is no further aim. Consequently, the more public role that women have in the modern world is of no consequence. For whatever reason, God commanded that learning gemarah is for men and not women, and like other gender roles ordained by God (dayanus, kohein gadol, smichah, serarah, child birth), this does not change with time.
The more modern (YU types, if you will) end of the orthodox world like simcha613 maintain the view held by many rishonim that “the goal of a person’s amaylus in Torah is not that he should simply study a lot of Torah; the goal is to be able to practice the Torah” (Rabbeinnu B’chaye on Avos 1:17 – there are many other similar sources). In other words, we study Torah in order to understand how to properly navigate through the world around us (a world we can and should enter and engage). Since we need Torah to tell us how to act in the world, the more we are engaged in the larger world, the more Torah we need to know and internalize. On this view, women not learning Torah sh’baal peh during the period of the mishna and gemarah makes sense – you don’t need to know much beyond practical household halacha if you spend most of your life keeping up the home. Indeed, as the gemarah says, for women to spend time learning in depth Torah sh’baal peh under such circumstances would be a complete waste of time (tiflus) since has no need of the Torah’s instruction to that extent in her everyday life. But now, when women (in some circles more than men) are in the work force and engaged in the larger non-Jewish world, they MUST learn in depth and prepare themselves to handle the challenges of the real world as God would expect them to.
nature of womens’ rol