Regardless of whatever obstacles are in their way, the Caliphate is the express goal of the Muslim Brotherhood. They have been operating since 1928, spawned most of the violent jihadist movements of today and appear to disagree quite vehemently with your assessment.
Believe me, I have worked for years on the Muslim Brotherhood. I was particularly interested in their involvement in the Mujahideen movement during the Soviet occupation of Afghanistan. I am aware of their meetings held in Italy that set up their international banking system. I am aware of the history of their penetration of Europe and the United States. Thus, when I say that even though they would welcome a return of the Caliphate itself, in this modern complex world with the numerous conflicts that exist within the Muslim world itself, that is a pipedream.