Why a control test is no longer regarded as a conclusive test? Which test is mostly applied in modern days to determine liability?

The control test as traditionally formulated was based upon the social conditions of an earlier age and “was well suited to govern relationships like those between a farmer and an agricultural labourer, a craftsman and a journeyman, a householder and a domestic servant and even a factory owner and a unskilled hand but the control test breaks down when applied to skilled and particularly professional work, and, therefore, in recent years it has not been treated as a exclusive test.