Judaism lacked its Messiah and the Kingdom he represented. In this sense, Jesus completed and transformed the traditions of Judaism. His action completed what was missing. The water turned wine has many meanings. God's kingdom was to be a feast with endless wine and merriment.
Water has a baptism motif, while wine is Eucharistic.
The sign in Cana was the first revelation of Jesus in John's gospel and the first opportunity for faith from his followers. The sign revealed the Kingdom and its Messiah. The Catholic Church has sacraments to express a mystery, something that we cannot fully understand. As Christians, we worship God the Father for creating and saving us. God the Father sent us his Son as a sign of his love.