Fintlocks were state of the art for centuries. They had their advancements and arms races just like we do with modern firearms. The American Kentucky/Pennsylvania Rifle might even be the pinnacle of flintlock technology, with it’s long, rifled barrel. It was twice as accurate as the Brown Bess the British were marching into battle with.
On the battlefield, trained soldiers could load them pretty quickly. And in guerrilla style tactics, many guys kept two or three loaded ones stashed nearby, to save time reloading.
The other thing about flintlocks is, especially smooth bores, you had to learn how to actually shoot.almost anyone can hit sub-MOA with a decent modern rifle, with a scope, rifled barrel, and hunting/competition ammo. With the old flintlocks, you couldn’t just “get by” and still put meat on the table. It took practice, and patience, and skill, and knowing how much powder worked in YOUR rifle, for the results you wanted. And it was a skill that most men in 17th and 18th century N. America were expected to learn.
When I first bought a flintlock (a left handed Traditions of some sort) I was quite humbled. I always considered myself a great shot, and even competed on the high school rifle team. But you could slip in your fundamentals, and still shoot a modern firearm reasonably well. Squeeze the trigger on a flintlock, and it doesn’t go boom instantly. You gotta follow through with the pull, keep your sight picture, and maintain your hold, while the powder in the pan burns and finally ignites the powder in the bore, and then, after what seems like an eternity, finally the rifle fires. I learned a lot about the importance of proper shooting fundamentals from a flintlock. Also took me a few weeks before I was able to hit the broadside of a barn from the inside!