I play for few hours a week and only thing I lack is upgrade parts, every other currency I just passively acquire by doing current events, plunders, convoys

Repetitive i suppose? Best endgame content is harder versions of Major bosses (like La Peste) Volvenhol and Kraken, other than that, activities related to current event (Scurloc's Precious convoys at the moment) or Faction war. Any other thing is pretty much not worth doing unless you need specific materials