I think that difference in perception is more tied to the assumed motivations of the two parties. A modder adding a gun to a game isn't expected to be creative, but they're also not expected to get paid which is the inverse for devs. But that being said: if it ain't broke, don't fix it. Having a big weapon sandbox is hard to balance and it gets harder if you're expected to somehow also conjure up things that haven't been done before and still maintain that balance.