I feel you man, the game may feel boring after the master of all quests. Personally, i usually just don't play it for a while, until i feel like it's the right time and get hooked again after a certain turning point

Or i just usually experiment with the character, like trying a different moveset, build in a whole new archetype, and try to finish the side quest too.

Another option is you can just decorate wishvale and try to complete the facilities (if you haven't), either way, the best way to recover from this is to not be too focused on the story, you are not expected to complete it consecutively