Anthropological note: It is important to read verses 11 and 12 together, lest one be tempted to see verse 11 as only a condemnation of excessive drinking. It is surely that, but the real condemnation is not of drink, but of the unrighteous excess of the religious festivals during which such drinking would occur.
It is verse 12 that gives us the surest context for verse 11, which otherwise becomes an unconnected verse, a solitary condemnation with no place in the larger text. This is a poetic text, not a speech, and the tighter exigencies of poetry are our clue to look beyond such solitary interpretations.
The telling note is the feasts, not simply the items in them. Such feasts in the ancient world do not refer to individual or family meals on a large scale, but rather to communal feasts, a large shared celebration by the community. Such feasts were tied to religion in the ancient world.
The condemnation is a feast that may superficially propose to be in the Lords honor, but in which the true Lord has no part. The essence of the message is the contrast between the things the feast does contain, such as drinking and music, with that which is does not contain:
“but they regard not the work of the Lord, neither consider the operation of his hands.”
It is possible that the feasts or festivals of Israel were being influence by their worldly neighbors, and Isaiah is condemning that intrusion of the pagan into an occasion that should have been purely for the Lord.
Robin Lane Fox describes the general order of the pagan festivals:
“The central ”cult acts“ for the civic gods occurred on the days of their festivals, Then, people processed, sang hymns and sacrificed in the gods’ honour. Sometimes they processed from a fixed point in the city to a particular shrine or altar: cities and temples had their ”sacred ways" and particular monuments long the route. By tradition, envoys would go out to summon other cities to attend certain festivals, a not inexpensive task whose cost, like the cost of secular embassies, was often borne by the envoys themselves.
In side the city, participants in festivals generally wore clean white robes and accompanied their own chosen animals for sacrifice. The temples were hung with garland and so, sometimes, were the private houses. Ritual worship was not confined to those who processed: people might pay libations or offer sacrifices on small altars beside their own residence. In a world without weekends, these festivals were the only “holidays.” (Fox, Robin Lane. Pagans and Christians. Harper & Row, San Francisco, 1986, p. 66-67.)
Both because of the possible excesses associated with the rare holiday and the ties of the festivals to the ostentatious display of wealthy men provides these feasts with the elements of potential corruption that apparently entered into Judah’s worship.