In the context of labeling emotions based on context-free still images of strangers, then yes humans are so inaccurate at this it would generally be a bad idea to assess emotions.
In the context of real life, where we know people, are interacting with them, and are reading cues from their whole body and their movement over time, then we're much better at assessing emotions and we'd be pretty foolish to ignore emotional signals.
In the context of real life, where we know people, are interacting with them, and are reading cues from their whole body and their movement over time, then we're much better at assessing emotions and we'd be pretty foolish to ignore emotional signals.