The Privy Council in singularis: the forerunner of the end of activism in the court's jurisprudence

The courts slowly started to adopt the doctrine of modified universalism, as evidenced in Cambridge Gas. Although the doctrine was distinguished in certain circumstances, i.e. in Rubin and Hew Cap, it was becoming more and more prevalent in the courts. This came to an end in the judgment in Singularis v PwC (1914) UKPC 36. Although the facts of the case did not allow for a more positive result, the dissenting judgements were clear that there is no doctrine of modified universalism as such. This questions the proper function of the appellate court, which in many situations ought to lay down policies. The European Court of Justice was an activist court for many years. Is there a legitimate reason for the Privy Council or any other appellate court to depart from such a path and take a more restrained approach? What would have happened to chancery if the courts had not been activist enough in the XIV century to remedy any deficiencies?