The Shia tafsir is that on the Day of Judgment, Allah will address the polytheists by saying to them when they are sentenced to punishment: where are those partners that you ascribed to me? Those idols you worshipped and believed they could help you? Where are they to save you now? God is mocking the pagans through this command. He’s telling them “call on your idols now, let’s see if they can help you.” It’s a rhetorical statement.
As for the “barrier,” that’s not an accurate translation. The Arabic word is موبقا which means place of destruction or perishing or pit of doom. Which basically means that these pagans have no way of seeking help from the idols.
I recommend this Tafsir: