I've never seen this one talked about but it's a legit pothole. In future trunks timeline goku dies of natural causes so he can't be revived by any dragonballs. That's apparently a rule. However in future arcs it's revealed that dende can alter the rules of the dragonballs at will. He can make more wishes, make them less powerful and even limit who makes them. Given retroactive knowledge of future events dende basically let goku stay dead. Of course this is a retcon but still that's a pretty huge plothole.