Never used a dsPIC myself, but 1 watt sounds like way too much. Do you remember the part number? Maybe 1 watt was for the whole dev board, not the MCU itself?
For SMPS control I've mainly used C2000 devices. The most powerful versions max out at around 1W. I believe all other "DSC" type microcontrollers (dsPIC, Kinetis, etc) should be substantially lower. And all these devices are built with fairly old processes, they're generally not aimed at low power operation.
For something basic like an offline converter a newer ARM-based MCU (like STM32L or STM32U) should have all the appropriate features with far lower quiescent power.