This metaphor contrasts the old teaching of the religious leaders against the new teaching of Jesus. The point is that people who are used to the old teaching are not willing to listen to the new things that Jesus is teaching. (See: [[rc://en/ta/man/jit/figs-metaphor]])
It may be helpful to add the implicit information. Alternate translation: "for he says, 'The old is better,' and he is therefore not willing to try the new wine." (See: [[rc://en/ta/man/jit/figs-explicit]])