Alan,
A lot of fly tying materials were not originally meant for fly tying. Innovative tyers found new materials and sometimes new patterns to use them on. Examples include Chadwicks 477 yarn, copper wire, Antron (carpet fiber), furry foam (Vellux blanket), etc.

Of course these materials can still be found (other than the Chadwicks) from their original sources. Once you start doing this, you have reached level one. This merely saves you money as a benefit of knowing some fly tying history.

If you realize that fly recipies are not burned into rock tablets, and you start substituting/altering recipies with new materials then you have reached level two. This can be a fun and interesting way to discovery better fish catchers.

Once you have an epiphany and realize that new materials can open the way to new recipies, then that is level three and you are walking in the footsteps of the fly tying innovators.

Is there a level four? Yes... at that level, you can catch plenty of fish on a bare hook