I'm with you, as most plants have nutrient requirements that are well understood and can be supplied by standard fertilisers as long as they meet the macro and micro demands of the plant. In aquatic systems these are reasonably well known.
The EI system is an up front method that states what, how much and when. I'm a little suspicious of those products that don't actually state whats involved, even though the end product may look pretty good. Faith is not enough in some cases. And if that wasn't enough the price of ADA products are well and truely beyond my meagre budget.

R