I bought my first flintlock in 1977...I built my first in 1988, took me 2 years and 200 hours...I killed my first wild turkey with the first, it was a .45 caliber...With it, I killed deer, squirrels, turkeys, rabbits, foxes and whatever...It's all I used for hunting back in the late 70s and early 80s...
Never had a problem with that gun not going off when hunting...The only time I'd have a problem was at the range when I didn't take time to sharpen the flint between shots because it wasn't critical...
When I built my .54 in the late 80s, I rebarreled the .45 to 40 and have continued to use it for my small game hunting...
Now, this is what I think is critical...My guns were both custom made, the first by Bob Watts in Atlanta...He was written up in Foxfire V...The second by me, they both have Siler locks on them...A well made lock for a flintlock will cost as much as some bargain production guns, and it is worth every penny...
You will not live long enough to wear out a properly tempered frizzen on a Siler flintlock....Yet, you can buy a brand new, cheap production flintlock and find that "bargain gun" won't spark...
If all you can afford is a cheap gun made in India then you can't afford a flintlock, stick with percussion guns...
Folks like your friend simply don't know what they are talking about or have had a bad experience with a cheaply made gun...You touched on this: the flintlock was invented around 1600 in France, within just a couple of decades all the European countries had them...It was used to ignite gunpowder until the mid-1800s, longer than any other system including what we use today...
Finally, Daniel Boone, died in his sleep when he was 85 in 1820...Think about that, all he ever carried was a flintlock...Yet he made his living killing deer and selling their hides for much of his life...Must have been a pretty good system as deer herds by the mid-1800s were just about wiped out by this system...
A well built flintlock doesn't "hammer" the flint against the frizzen...The frizzen spring has only about 3 pounds of pressure holding the frizzen shut and flips over easily to scrape the flint over the steel to produce sparks...
If you do decide to buy a production flintlock at least buy one that you can remove the original lock from and replace with one of the well made locks available to the custom makers...
A well made flintlock is a thing of beauty and very reliable...A cheaply made flintlock that is imported isn't worth having...
Just some observations from a fellow that has been shooting these things for almost 35 years...