I just recently beat the game, and looking back now there wasn't a lot of elements that I disliked. I guess some of the gym bosses were too hard if you didn't have the right party, but it was simply a matter of getting gud and recognizing patterns. It was an overall enjoyable experience.
However a few things I didn't like was how early on I kept constantly reaching the badge level limit and had to use what seemed like hundreds of common candies. It feels like a waste getting into battles only to end up lowering your pokemons level due to the constant overleveling. I also really didn't find the south aventurine woods puzzle fun, the entire process was tedious and required far too much backtracking. There's nothing wrong with backtracking if done right (side quests, events, etc) but it becomes a chore when a puzzle involves a repetitive forest area that is also the size of most wards. That much area used for a puzzle was a bit overkill and a waste since you never touch the forest again.
