How much does omitting articles really cost you on band 7 and above?

The Voccle and Diglot lists both flag article omission as one of the top persistent errors for Korean learners, and it directly hits the grammatical range and accuracy descriptors. In Task 1 or Task 2, a single missing or wrong article can change whether a statement is general or specific, which examiners notice even when the overall meaning seems clear. I am looking for any proven micro-routine that targets articles without adding more slang or high-frequency vocabulary practice.