Artsier is an informal word that describes someone who leans towards the artistic and creative side. However, there are many antonyms or opposite words to describe someone who is not artsy or creative.
Some antonyms to the word artsier include unimaginative, uncreative, conventional, conformist, average, mundane, and typical. Other antonyms for artsier are pragmatic, practical, analytical, and logical, which describe people who prioritize functionality and rationality over aesthetics and creativity.
Therefore, if you want to describe someone who is not interested in artsy or creative aspects, you can use these antonyms to define them more appropriately.