I think most of what has been invented by certain people who first popularized it or patented it would eventually have been "invented" by someone else. Do you think no one would have come up with the idea of an elk hair caddis without Al Troth? Perhaps years later, but I think someone would have.

It is the nature of mankind that someone is always experimenting with "new" ideas, techniques, materials, etc. in fly fishing that leads eventually to new generally accepted flies or fly patterns/styles. In my opinion, anyway.