Pitch peak or plural -s: which one costs you Band 7

On a Korean test-prep forum I keep seeing the advice to focus on intonation first. But in an IELTS Writing Task 1, a missing article like 'the' in 'the number of visitors' is a clear error on the rubric, and a flat pitch is not even marked. If you cannot consistently place -s and articles, the prosody work only distracts from the structural errors that actually lower your score.