God totally can save his people, he just doesn't want to cuz they've been sinning left, right, and center.
They've been abusing their legal system, launching frivolous lawsuits, and lying about a whole bunch of stuff. This, says, Isaiah, is like hatching serpents' eggs (since it only makes more serpents) or weaving a spider's web (which seem like a good idea, but are too insubstantial to cover them as clothes. We could've told them that).
Basically, their bad deeds lead to more bad deeds, and their protestations of innocence aren't fooling anybody.
They've also committed more horrible sins, like murdering the innocent. Thanks to their sinful doings, the people (it's now in the first person plural, so it's all about "us" and "we") wander around in the darkness, begging for light and stumbling through the night, growling like bears and moaning like mourning doves.
The people confess that they can't find salvation, since their sins are so great that there's a wicked (pun intended) high barrier between themselves and God.
God, however, is going to solve all of this. He dresses up in righteousness (it looks like white taffeta, to the untrained eye) and vengeance (more of a black velvet)—like a soldier putting on armor, heading out to defeat the evil.
He'll deliver swift justice to the wicked but forgive everyone who repents. Seems fair.
He promises to redeem Zion and says that he will put the spirit that has spoken these good words into the mouths of the people and into the mouths of all of their descendants forever.