There are several synonyms for the phrase "falls down on." Some common alternatives include "doesn't measure up," "fails to meet expectations," "underperforms," "falls short," "disappoints," "let down," and "misses the mark." Each of these phrases can be used to describe situations where something or someone did not live up to the standards or goals that were set out. Whether it's in terms of job performance, athletic ability, or even personal relationships, these phrases can help convey the sense of disappointment or frustration that can arise when expectations are not met.