There is a strange trend of downplaying Byzantine heritage.. for instance modern Greek society seems to uphold the ancient Greeks much more, when in fact there are much closer ties to the Byzantine... a few hundred years ago it wouldn't have occurred to any Greek that they are connected to the ancients, and this trend has started with European Romantics.

But they did produce significant art and science, and especially architecture: https://en.wikipedia.org/wiki/Hagia_Sophia https://en.wikipedia.org/wiki/Byzantine_science

There would have been no transmission of the classics without the Byzantine, and possibly no Renaissance in Europe.