Actually, in the hands of a skilled user, a musket could fire 2 to 3 rounds a minute. (https://tinyurl.com/y7jqulpv) As for barely killing a squirrel, they were used to kill a lot of soldiers. (https://tinyurl.com/ybobvug4). Since your initial premise is completely and demonstrably false, is it possible that your conclusion is just as false? Do you remember the quote about a house built on sand?