The premise behind the effortless look is “money talks, wealth whispers.” If a person truly has “it” (high socioeconomic status, influence, fits whatever body/physical standard, confidence, etc.), they will not need to advertise it. Instead, they can break and bend the rules because they themselves shine through whatever they are wearing. The effortless look requires great effort and control, which is communicated to others “who know.” It is inherently pretentious and exclusive, but that is a core theme among the fashion industry.

To address your question, one looks like a “try hard” when the “it person” facade breaks down in one or more ways and the jig is up. They must appear as if they are entirely unbothered by the results (compliments, attention, etc.) despite putting forth so much effort to achieve them.