What does Isaiah 17:11 mean?
Through Isaiah, the Lord has told His people Israel that they have forgotten the God of their salvation and refuge. Because of this, they have sought salvation in the worship of other gods (Judges 2:16–19). They have also looked for refuge in alliances with other nations (Isaiah 17:1–6).The prophet compares this to planting a good plant that provides good fruit by using a cutting or "vine-branch" from a stranger (Isaiah 17:10). The person in this imagery succeeds in making the plant grow and blossom, but there is no harvest. They have spent all their time, energy, and attention on a plant that returns nothing. This is what worshiping false gods is like. Even when it appears to be the same as honoring God, the result is nothing but emptiness and hunger.
Israel experiences the consequences of forgetting who the Lord their God is. The Lord who saves them is also the One to bring a day of judgement full of grief and pain.