I don't buy into all the high end gear for fly fishing myself. I imagine it makes some difference but less difference than the ability of the fisherman and the conditions. You can say that about a lot of things really...
It drives my dad nuts that I get by on a trip with a single rod (with the other in the truck just in case) and a small convertible belt or chest pack with a assortment of flies appropriate for the area, a match book of twist on lead weight, spare strike indicators, fish hook remover on a retractable line, dry fly floatant, a small tube of sun block, old razor sharp Swiss army knife for gutting fish, a couple of spare leaders, and a micro leatherman with pliers also on a retractable line for utility work and bending down barbs if doing catch and release. Plus a single AAA led flashlight and a water bottle in a cargo pocket. The whole thing weighs about a pound and a half. This is of course close to civilization or at least to the truck fishing. If going a ways I use the same little pack plus my small hunting pack with a poncho and some survival gear minus the hunting specific stuff.
He goes all out with a huge fishing vest plus camelback pouch that he manages to put something in each pocket and weighs about 25 lbs. I have one of those he bought me that I have never used. He also has his "bling" (his words, I grit my teeth when he calls it that) around his neck with snippers, pliers, fish hook remover, eye glass cleaner, floatant, and god knows what else. He bought me one of those too, I took it apart for the retractable line deals for my small pack.
We stay roughly even on # of fish caught...