Jehovah shows what trouble he has had in bringing up His child. Judah behaves worse than a brute beast. Their heads are not in the right place. None of the sins of God's people in Isaiah's day are new. Nor are any of the sins we commit today new.
Sin is sin.
They were trying to find their own remedy to escape punishment from Jehovah. They were trying to worship their way back into fellowship. Some who go through the motions of worship are rank hypocrites. There are many inventive ways of removing from the mind any fear of judgment or responsibility to Jehovah. Become totally liberal and say there is no sin.