Many excellent diagnostic tools are next to worthless.
Because the value of a diagnostic is limited by the value of the therapeutics it supports. Most therapeutics, including nearly all monospecific drugs, are next to worthless. Moreover, most monospecific drugs cannot work by definition.
However, fully powering both sides of a metabolic pathway (a metabolic analogue of bispecific drugs) can work as a therapeutic in principle. No one is even trying this approach – so typical of mankind.