Diagnosing more people does not necessarily mean diagnosis is improving, especially when the criteria are purely subjective (and there are perverse incentives for pharmaceutical companies to diagnose more people)
69% of the DSM-5 task force had ties to the pharmaceutical industry.
Diagnosis rates grow each year, and the number of ambiguously defined mental illnesses increases with every revision of the DSM. These data points are used as justification for further increases in funding, which in turn increases diagnosis rates.
This pressure increases the pressure to make it so more of the population is defined as being mentally ill so they can get medical treatment.