Bede

And no one having drunk old wine, immediately desires new, for he says, "The old is better." This signifies the Jews, to whom, being steeped in the dregs of an old way of life, the precepts of new grace had become tainted. For indeed, being defiled by the traditions of their ancestors, they were by no means able to perceive the sweetness of spiritual words.

On the Gospel of Luke ↗

Bonaventure

This same thing was likewise expedient on account of the disaccustoming of affection: to designate which He says: And no one drinking the old straightway desires the new. And He gives the reason for this on account of the judgment of the senses, when He says: For he says: The old is better. In this, through a similitude in the delight of drink, He wishes to show that our affection is not immediately delighted in observing new things, unless it is gradually led by the hand. …

Commentary on Luke, Chapter 5 ↗