Superficially, it is similar to conky in concept, but with very different primary points of focus. whilst conky excells at having lots of info on your desktop in the background, eww might not be optimal for that. On the other hand, eww is generally a lot easier to get visually appealing main-point-of-focus widgets in, for overlay dashboards, media/volume controls and of course bars. Eww was and is generally designed to be more or less "two-dimensional polybar", both in its original design of widgets and the state architecture.

Being written using GTK and thus also styled in GTK CSS makes a big impact here, of course