My primary goal with ECSS was to isolate styles as opposed to abstracting them.

Ordinarily, it makes sense to create CSS classes that are abstractions of common functionality. The benefit being that they can then be re-used and re-applied on many varied elements. That's sound enough in principle. The problem is, on larger and more complicated user interfaces, it becomes impossible to make even minor tweaks and amendments to those abstractions without inadvertently effecting things you didn't intend to.

A guiding principle with ECSS therefore was to isolate styles to the intended target.

Depending upon your goals, even at the cost of repetition, isolation can buy you greater advantages; allowing for predictable styling and simple decoupling of styles.

A further advantage of isolating styles is that designers can be encouraged to bring whatever they need making, without necessarily feeling encumbered by existing visual patterns. Every new module that needs to be coded can be a greenfield. I found that I could code out designs far faster when starting from scratch than attempting to build them from any number of vague abstractions.