That period is bracketed by the sudden end of the Mycenean civilization, and the return of writing with the "invention" of the Greek alphabet. But this periodization, and calling that period "dark age", mainly shows our bias towards written sources. Throughout that period and beyond, the Greeks culture was essentially all oral, and if we ignore that oral component and only look at the written sources, we essentially don't see that period at all. The early examples of writing in the archaic period were all in verse, because poetry was an efficient way of preserving text and stories in the oral tradition. The Homeric epics were recited, sung to music, perhaps danced to, throughout the Greek world for decades or centuries, before they were put down in writing. There is no reason to believe that society did not function without/before the written word. Religious festivals where choruses performed poetry to music and dance, for example Alcman's Partheneion, existed both before and after the end of the "dark age". Elite men enjoyed meeting, drinking, and listening to poetry before and after the end of the "dark age". We have some written sources at the beginning of the archaic period, and they all point to a society where the written text was really secondary to the spoken word. In general, the Greek civilization during the "dark age" was probably as vibrant and rich of culture as the one of the following archaic period, but we just don't have extant written records of that period (or of other civilizations in other parts of the world during the bronze age).

For a fascinating overview of ancient Greece as an oral society, I highly recommend Rosalind Thomas, Literacy and Orality in Ancient Greece. Not only it helps you see specifically the Greek civilization of the archaic period beyond the limited written sources, it also helps understand oral civilizations in general, and essentially all pre-modern civilizations were primarily oral.