I have found that the best two times to go fishing is when it's raining and when it's not. (I think it was Patrick McManus who said that.)
I think it was John Gierach who said something similar to this: I got mine on nymphs and he got his on dries because that's how we wanted to get them.
Too many people over-thinking things. Voo-doo and whoo-doo. Too much, I tried this color and caught more fish. I tied a fly this way and caught more fish.
My biggest trout have come in the heat of the afternoon in July. The sun high over head, sweat running down my back, a dehydration headache working my brain. I've spotted the huge browns sitting out in the sunlit water. They even rose to a dry. Why: nobody else was around. Other anglers were waiting for the cool evening when everyone knows that the big browns come out to play. Besides, it's too hot to be fishing. Well, when everyone else shows up for the evening fish, they spook the big browns and send them into the deeper pools, up under the plunge pools and undercuts.
I think there are a lot of experts out there (I'm one) and they all have their flies, their techniques, their theories, and their experiences and their opinions whether you want them or not. Listen carefully, try a few things out, find what you like, and then do it.
Okay, lets make it even more simple: wet flies on rainy days and dry flies on clear days.