I hestitate to call anything "wrong" in terms of trying a product and seeing if it works for you. Just about anything is worth a try, and everyone's ichthyosis is just a little different. So while there are certainly some commonalities (a product or ingredient that works well for a lot of people with ichthyosis), your personal experience may always vary.
I think it was worthwhile for you to try the Neutragena shampoo that you did---unfortunately, you found out it didn't really help.
Yeah, next time you're shopping for shampoo, you might want to give one of the other Neutragena shampoos a try. T-Sal is definitely the strongest of the Neutragena shampoos (in fact, some people with mild ichthyosis find that it's too strong for them). Maybe you'll have better luck with one of those. The PDS shampoo is also very potent.
So much is still trial-and-error when trying to figure out what will help your ichthyosis.
Hope you find something that you like,