Accuracy of shooting was never really an emphasis for musketeers. Most smoothbore muskets didn't have sights. It just wasn't seen as an issue because a lot of military doctrines at the time said the role of muskets was to fire one concentrated volley into the enemy at close range right before a bayonet charge, which was supposed to be the real fighting the line infantry would do. Regiments would usually have a company detach from the formation to fight as skirmishers in loose order ahead of the line - these guys were expected to take more time to aim, but this was just a temporary role they had to fill, not something they were expected to be super proficient at. For doctrine makers the main tool for attacking enemies at range was artillery.