Anything worth doing is probably also worth doing half-A#$ed
The amusing self-negating, self-contradictory, and somewhat derogatory forced marriage of the concepts of worth and a slang term for something not worth much. This is probably best understood as an indirect, disguised, maybe passive-aggressive?, argument that whatever is being discussed is not worth doing.
By definition, the original statement cannot be true unless in all cases there is nothing worth doing. This proposition does not seem to be a truth.