The Medieval era may have been a brutal time of prolific warfare, but it certainly did not lack cultural production and innovation. From the Vikings carving runed stones in the distant lands they sailed to, to towering, spired wooden architecture, to beautiful, richly embellished jewelry inlaid with gold and gemstones, art advanced and preserved the Medieval era’s culture. The Book of Durrow and the Book of Kellis and other important religious manuscripts showed an introduction and incorporation of words into art and art into literature. Crucifixes, crosses, and beautiful Abbeys were erected, such as the High Crosses of Ahenny and the Abbey Church of Corvey, all demonstrating great care and intricate design.
So yes, to say the “Dark Ages’ were a time of declined culture would be quite incorrect.