Christianity was not locked in during the time of the Byzantines and in many cases discussions were common about it's different interpretations. Monphysitism, Iconoclasts, various flavors of Arian (named for the monk Arius), etc. were all floating around.
Constantinople had a reputation for having constant theological debates; writers mentioned how common townsfolk were debating the nature of Christ, etc.
Historically, looking back at them we see "unenlightened" folk -- perhaps the way future people, the ones who survive WW4, will look back at us and our debates about race and gender -- but at the time they were wildly well educated and highly versed in religion, politics, and philosophy.
And they did have science -- we have yet to fully understand Greek fire. Innovations in armor and horse breeding created the Cataphracts, based on Eurasian horsemen that the Byzantines routinely clashed with.
And, as the article points out, they smuggled silk and created a new industry from scratch. We scorn them for not being as advanced as we are 1000 years later but for a while Constantinople was, to quote Napoleon, "the city of the world's desire".
