Does an engineering paper have to improve on the state of the art quantitatively in order to be publishable?
In order to be publishable, a scientific work needs to provide evidence that it advances the state of human knowledge.

Direct quantitative comparison to the state of the art is a relatively straightforward way of doing this, but there are many other alternatives.  For example, one might also provide mathematical proof of a difference in expected scaling or demonstrate a qualitative property that is not present in current systems.

The key in every case, however, is that there should be clear evidence provided of some sort of value that other investigators are likely to find to be of interest.