Nationalism and nation state is going away not because of pseudo-Islamism but gradual integration of the global economy and political structures but nations will still exist in some way having one huge Islamic state would easily fall apart due to cultural differences and also certain differences in practicing religion too as well this is a warning I give to my country men a united Islamic block would need a single country or powerful country to lead it and I dont see that at the moment
Caliphate collapsed ever since the Abbassid caliphate decentralised and gave way for independant states or empires.
Abbasids basically became the religious symbol while most Muslim states like the Seljuks and Ghaznavids pledged alleigance to the Abbassids but ruled independantly. When the abbassids were gone in 1258 they still held a religious office in Cairo under the Mamluks until they gave it to the Ottomans in 1517.
Caliphate today wont work for a multiple reasons because Muslim countries have evolved due to a wide range of factors. Many have become nation states.
Saudi Arabia and uae also do not qualify as a caliphate neither does Morocco despite the the King holding Amir Ul Mumineen.
I think some Pakistanis hold this idea of Erdogan bringing the caliphate back and the Ottomans. A lot of Muslims nowadays regardless of Turk or Non Turk dont believe in bringing back dead empires.
A lot of religious scholars believe the Muslim Empires collapsed was due to Allahs will and we should not argue it.
Ottomans, Mughals, Ummayads, Abbasids, Timurids, Seljuks, Al Andalus, Mamluks, Ghaznavids and various other Muslim empires collapsed and became part of history. Its best that they stay that way.
I dont think our forefathers want us wasting time in trying to bring them back.