I wouldn’t describe critical psychiatry as having failed.
It seems to me that the CPN has largely succeeded in doing what it set out to do: keeping alive the question of whether mental illness is best understood as a disorder of the brain and challenging the assumption that physicalist explanations should automatically take precedence.
The search for biological explanations will no doubt continue, as many regard that as an important endeavour. But perhaps the continuing contribution of critical psychiatry is to ensure that the debate remains open and that psychosocial, relational and meaning-based explanations are taken more seriously rather than treated as secondary to biological ones by default.
In a field where there is a constant temptation to declare the argument settled, keeping the question open is important in itself.