When you pull underwater critters from their habitat (mayfly, caddis, stoneflies, scuds, dragons, midges) they, for the most part, are smooth looking and segmented. They often look like some creature from a science fiction scene…in a way, I guess they actually are.
I am not presenting this post as an end all recommendation on fly pattern design. My suggestion is to recognize the options of fly pattern design: exacting imitations or suggestive (scraggly) of life imitations. Have both and know how to present the options in the most appropriate manner. Where does that insect or critter reside subsurface and how does it move under control or out of control.
Here you have the scraggly Gold Ribbed, Bead Head Hare’s Ear Nymph with the buggy, scraggly thorax. Also, the lower left pattern is a nymph pattern that is somewhat representative of a Caddis or Scud. Below right is the simple, streamlined, only so slightly scraggly Czech Nymph. All catch countless fish. Have both and again pay particular attention to where these insects live…how they move (dislodged and drifting, climbing/rising, crawling, swimming).