The spanner in the works of Roman-Orthodox reunion
Like I said, the foundation and scope of the Pope: divinely instituted with universal jurisdiction or man-made rank with limited jurisdiction? (Not the same as the Western liberals who don’t like him because he’s Catholic and thus doesn’t claim a power to change things as they’d like.)

Romanism [sic] and Byzantinism [sic] both make claims of ecclesial ultimacy.

Right, both believe in an infallible church.

But their respective claims are mutually exclusive, as the former insists on papal supremacy and the latter on the received faith of the ecumenical councils. Thus, despite whatever superficial similarities Rome and Byzantium may have, they are different ways of understanding what it means to be catholic.

— Dan Dunlap

I wouldn’t say they’re superficial like many Orthodox controversialists say but deep like Soloviev said, but yes, that’s the insurmountable problem dividing what’s nearly the same church (which is why on the ground in so many places today they’re obviously not the same church).