I have often pondered this parable, wondering what it might mean. I understand the new cloth / new wine analogy well enough. But the spiritual application has been the puzzle. So, the new covenant is fit for a people with a new nature to accommodate that new covenant. The new covenant is all about the Torah written on a new heart, so that obedience is a matter of nature rather than obligation.
Everyone, when all they have had is old wine, says the old is better. But in the new birth of the new covenant, the new nature is not compatible with the old nature, just as the new cloth is not compatible with the old, and the new wine is not compatible with the old wine skins. When you try to mix them, both new and old are ruined.
You might say that Yeshua and His disciples were not really eating and drinking with people incompatible with them, because the repentance of the sinners put them in the same class as Yeshua and His disciples, the “new” class.
And even though the Pharisees and doctors of the Torah were the religious experts and religious professionals of the day, they were more like a people incompatible with Yeshua and His disciples, because their non-repentance put them in the “old” class. They had to receive the new nature, and new heart, of the new covenant first; but it was hard for them to admit that the new was necessary, and good, even in the face of all the proofs the Spirit of God and the power of God was constantly showing in Yeshua’s life.
So does Yeshua discard the old covenant? It is not the commandments, or YHVH’s standards of righteousness and sin that has been discarded, and this is the great lie the enemy had lied to the people of God. We saw that the renewal of the covenant changed the place the commandments were written, from tablets of stone (old) to the tablets of the heart (new). The agency of change is repentance and trust, faith in the saving blood and work of Messiah Yeshua.
As the Scripture says, Humble yourself under the mighty hand of God, that He may exalt you in due time! And this the tax collectors and sinners were willing to do, and many Pharisees and doctors of the Law could not (but many, after the Resurrection, did. There is nothing like angels tearing down a six-inch thick veil so that the Most Holy Place and the presence of God was no longer separated from the people, to cause you to re-examine the Scriptures, and discard your unbiblical assumptions).