Is there a setting that needs to be changed before you can item jump consistently? Or was it patched? I must have tried hundreds of times, but only got it a handful of times. All the speedruns and tutorial videos on YouTube make it seem super trivial. Literally just jump and drop the item at the same time.

You need very high FPS to perform item jumps successfully. Timing is also important but you need (1) a wall with the right angle and shape, (2) proper inputs, and (3) the distance you get is proportional to your FPS (not on all item jumps, which is why some work on 60fps too just as well - but I'm not going to start explaining the entirety of the physics engine to explain why that is)