Rulings that are tied to custom change with time and place.
In other words, you can't simply stick your head in a book and just copy-and-paste fatwas in the past as though you're arguing the same thing they are.
In fact, Imam Qarafi (d. 684) strongly criticises those who dismiss changes in custom when applying such laws, labelling endless copy-and-pasting fatwas as misguidance and ignorance.
A textbook example of this is the issue of women's attendance in the mosque.
The default ruling, as demonstrated in the time of the Prophet (peace be upon him) in both action and statement, is permissibility.
This is indicated in the report of the Prophet (peace be upon him) saying, "Do not prevent the women of God from God's places of worship." (Bukhari and Muslim)
When Abdullah ibn Umar relayed this statement to one of his sons, his son argued that he will prevent them, so Ibn Umar rebuked him strongly saying that he just quoted to him the words of the the Messenger (peace be upon him). (Muslim)
One of the wives of Umar ibn al-Khattab would attend the Fajr and Isha prayer. When asked why she attends despite knowing her husband does not like it, she said she knows why Umar does not stop her from going, and that is due to the statement of the Prophet (peace be upon him). (Bukhari)
Now if someone acknowledges that the default ruling in the time of revelation, as explicitly stated by the Prophet (peace be upon him), is permissibility of women attending the mosque, then the only question is whether there is any strong reason to depart from this default status - in a way that considers both short-term and long-term harms in preventing women attending mosques, and that is actually consistent with how women engage in society and occupy spaces in every other domain.
And any harm you do actually claim exists must not be the same harm that already existed in the time of the Prophet (peace be upon him), since that was present in the time of revelation yet was still not a reason for prohibition. Mere attraction between men and women always exists, and it existed in the time of revelation and was not a sufficient reason for prohibition.
If this assessment is not thought out, then one is simply altering the ruling set out by the Messenger of God (peace be upon him).
Furthermore, changing the default ruling of permissibility based on some preventative measure (Sadd al-Dhari'ah) is a ruling from necessity, as it is effectively altering something permitted by Allah and His Messenger (peace be upon him) - something which requires great caution (and its application is restricted based on the principles of necessity).
And you can't simply copy-and-paste some fatwa in the past. They're not speaking about your context. You're the one speaking about your context, and you're the one liable for your assessment.
As for the famous statement of Aishah (may God be pleased with her), not only is her statement not an explicit prohibition of women attending the mosque (rather than it is a rebuke of the actions of some women in attendance), but the other Companions also did not view it to be a reason to prevent women from attending the mosque. In other words, if some women happen to be doing something they should not be doing, then simply address that action rather than a blanket prohibition.
In any case, I'm sure today there are many mosques that provide access to women, and those that don't are simply losing their female audience who will attend those mosques and learn there. So once they realise they're shooting themselves in the foot, I'm sure they'll come around... eventually.
