they understood me" is not good enough

The common advice to "just focus on communication" ignores what happens when a missing article or a dropped plural actually shifts meaning in a written contract, a formal email, or a job interview. Korean has no article system and often drops subjects, so L1-transfer errors are not random; they are predictable and, left unchecked, fossilize into habits that a reader will not ask you to clarify. Correcting the rule once, explicitly, is faster and more reliable than hoping exposure alone will fix it.