I have actually found that sometimes doing nothing can be better for the fish than breaking out the meds at the slights sign of ich - I witnessed many fish beating ich without any further interaction from my end than feeding them well.
The real risk is misdiagnosing something more sinister for ich - which is unfortunately quite common and even happened to me.
I personally stay clear of copper sulfate because in the past I've only made bad experiences with it. I've never tried chelated copper though.
I would just be too lazy to measure copper levels twice a day when on the other hand checking the salinity of a hyposalinity tank with a refractometer is just a second affair.
Cryptocaryon is in my experience usually more of a nuisance than a serious thread, and if it gets out oh hand and I have to treat it, I prefer hyposalinity or TTM.
Copper has most certainly it's value in treating Amyloodinium infections on fish intolerant to CP, but there have been Amyloodinium strains found to be immune to copper at levels that would do the most copper tolerant fish in.
In the past copper was the go-to catch all cure and if you are not sure what you have to treat it may actually be still an option. I just don't think it is the best option in most cases.
As for Joyce Wilkerson, I have her clownfish book and there are many things in it that I do not agree with. One of them is that you need rotifers for raising clownfish larva. I've raised thousands of percula, ocellaris and clarkii that were raised entirely with brine shrimp and frozen Cyclops.
The statement that copper causes sterility may very well be another unfounded myth that lacks any scientific basis.