I find collectables and treasures that do that the most annoying. At least most games with sidequests have journals and markers that can remind you exactly where a particular quest is so when you have what you need to progress you can actually know where you're supposed to go. With collectables and treasures they're interspersed throughout the map without any markers provided to so much as let you know they're there even after you locate them, and on top of that most of them quickly become useless unless acquired immediately. The end result is that you either need to have really really good memory, a guide, or have to run around the entire map over and over every time you obtain a means to obtain some of them. At the very least there should be markers placed on the map whenever you locate a collectable or treasure, preferably one that identifies exactly what's needed to get through it whether you currently have it or not.
I never had a problem keeping things in mind for the South Park games, remembering most of the areas doesn't seem that complicated. On the other hand, I also wouldn't have a problem with the game including a way to skip this content if there are people it truly seems to annoy. I mean, I spent $80+ on the game and the season pass; I feel like I have a right to play it the way that is the most enjoyable for me. Others should have that same right.
Take out all the side quests, though, and you have a pretty sparse game.