The Mississippi flyway still sees a lot of duck hunters, and a lot of ducks and geese, just not a lot of folks doing it for the reasons laid out by several here. Canada geese are so abundant here as to be a nuisance, folks hunt them, but we have made it so nice for them that the population never seems to drop. Other game birds and small waterfowl have a tougher time of it through loss of habitat, and, worse, almost no control of the predator population. Coyote populations have exploded, bear numbers here in CT. are unchecked, and the worst for the game birds, the protection of birds of prey has done its job and bird of prey populations have soared (ha ha, get it), but now that the numbers have recovered I'm sure there is no hope of getting those numbers in check so grouse/partridge and smaller ducks and such will suffer.
I know you think all is superior there. Can the average Joe or Jane just go online or to the local sporting goods store and buy a license a gun and some ammo and go hunt? Most states here have public hunting land, and studies have shown that it is NOT the hunters that have reduced game population numbers, so one can take a safety course, buy the license and tags, buy or borrow a gun/bow, get some ammo, and go hunt.
Unfortunately if a lot of people here don't wake up real quick, we are going to loose that freedom real soon. Regardless of what one hunts with. Hunting and shooting is on it's way to becoming an activity for the wealthy and privileged.
The attitudes that contribute to the lack of muzzleloading hunters in general and, now that you bring it up, muzzleloader use for waterfowl hunting in particular, are not and will not help our cause.
I agree that certain technical difficulties have been foisted upon the muzzleloading waterfowl hunter. But, beyond the shot material restriction challenge, isn't working with and overcoming those difficulties part of the allure, part of why we do this? The trophy hunting t.v. show, treating the taking of game like it's a competition with high fives and whooping it up over some antlers or a large bag limit taken, shoot more game and farther and easier with the latest greatest gizmo, commercial mentality makes using a muzzleloader not only unfathomable for many modern hunters, it is not even on their radar as a possibility. I think this mentality/attitude issue is compounded for waterfowl hunting with it's already unique challenges.