It looks like most of the “boring bits” for people fall into one of four categories.
The game system itself taking too long, aka the dreaded 30 minutes of fun packed into 4 hours. Long combats, measuring distances, combat continuing after the outcome is a foregone conclusion.
Other players causing problems, as in taking too long to decide, getting into pointless fights, the referee presenting static or boring encounters, etc.
Non-story-related time wasters, like all the pointless RPing with shopkeepers or tedious travel.
Bookkeeping, the ever present tracking of weight carried, ammo, rations, etc.