It depends on how you look at it: All live worms and minnows will catch fish of some sort and hand tied flies are not "alive" and must be tied so that they have "movement" to make them look "alive" and then they may attract and catch fish. I have watched many fish a fly like it was "bait". By that, I mean they just tie it on and cast it into the water anywhere and wait for the fish to find it and eat it as if they were using live worms and minnows. The fly must be presented to look "alive" and fished where the fish should be before it can produce results. I am a firm believer that any fly will catch fish if it is "fished/presented" correctly. A great fly does not "catch" fish. A good fly fisherman/woman "catches" the fish using the fly. A lot of people just do not want to take the time to learn to "read" the water, observe their surroundings, put their fly where they feel the fish are or should be, or learn about the habits of the fish species they are after. A lot of new fly fishers want to be as good as the person who has spent many years perfecting their style and they feel this person has the "secret" fly that always produces results. If people would understand that the fly rod, the fly line, the leader, the tippet, the fly reel and the fly does not "catch" the fish. The "fisherman" catches the fish. All flies will catch fish if the person using them has taken the time to learn how to fish......There is no easy button to become a good fly fisher person. It takes your time and dedication to learning how to "fish".
Warren
Fly fishing and fly tying are two things that I do, and when I am doing them, they are the only 2 things I think about. They clear my mind.