Well you could hit the broad side of a barn- like they did in the Napoleonic Wars for while- then you start choking on all the smoke and someone rushes you on a horse or with a bayonet. Its a real bummer
And yes, a rifle does have some accuracy- until the powder clogs it up which is why they used muskets for so long
But certainly by 1900, no one really had a clue of how to fight a real stand up engagement of large heavily armed forces. Everyone's manual was out of date and there's going to be a lot of learning to be done
Except that the Battle of Inkerman involved the Allies winning precisely due to heavy and accurate rifle fire.
The British were also able to shred cavalry attacks at a range of nearly half a mile in the Indian Mutiny, so a horse doesn't help.
As for the powder clog issue, that's why the minie ball is used. Since it expands when fired, it can be smaller and still fit down the barrel - and, as such, clogging is a bit less of an issue.
As for broad-side-of-a-barn, that depends entirely on training.
American platoon in the ACW: 40 rounds fired at a barn 100 yards away, four hits - of which one at the height it wouldn't just go straight over someone's head.
British soldiers in the same period: start training at 150 yards, even the third class soldiers can score roughly 50% hits on individual men at 300 yards.
The smoke issue is an interesting one - it's worth remembering that the British used open order, so the density of the troops was 1/2 to 1/3 that of a single close order line and perhaps 1/6 that of a three-deep firing line.
When you have that line firing once every thirty seconds or so during measured fire, then it's really not much of a problem.
We also know that the same accuracy training made volley fire - on the rare occasions it was called for - devastating. There's an account from the Crimea of a Russian cavalry charge which got shredded by what amounted to a single volley fired at close range, where the hit rate was better than one in ten.
But, frankly, when your army is the only army in the world at the time where any line regiment can shake out into skirmish order and pick off the men trying to serve their guns from beyond the effective range of those same guns... that's something impressive.
(The Connaught Rangers did this in the Crimea at 600-800 yards - I believe it's Inkerman, which was a battle fought in poor visibility conditions.)