The idea of unifying Islam is a recent invention and a bad one

Faisal Devji in Aeon:

Even sophisticated people speak of Islam as if it is one thing. The devout, the haters and the indifferent often share this belief in Muslim unity. And for them all there is no greater display of Muslim unity than the Hajj.

The Hajj, the pilgrimage to Mecca, is a grand and dramatic display of Islamic brotherhood without racial or national bounds. Or so it appears from the outside. But this way of seeing the pilgrimage is relatively new. It seems to have originated in accounts by 19th-century European travellers. The most active and best proponents of the myth of the Hajj have always been notable Western converts, such as the Galician Jew Leopold Weiss, who became the Islamic thinker and Pakistani politician Muhammad Asad, or Malcolm X, the activist for equality in the United States, who wrote about the Hajj in rapturous terms. Given that Saudi Arabia had abolished slavery only a few years before Malcolm X’s pilgrimage, his view of the Hajj as the embodiment of a longstanding and more just alternative society might have been a bit naïve.

Muslims themselves have also taken up the claim that the Hajj represents a kind of ideal society, free of the prejudices and divisions that dominate the profane world.

Proponents of the Hajj as a social ideal speak of the brotherhood it enacts. Brotherhood is a common and powerful metaphor of closeness. As all brothers know, however, brotherhood is rarely if ever about equality.

More here.