Deku is a library for rendering interfaces using pure functions and virtual DOM.

Virtual DOM is valuable because it allows you to build apps without thinking about state transitions, with performance that is generally good enough

This is exactly what we need the vDOM for — we might not need it for reactive state updates, conditional rendering or list rendering, but as long as we have it we can treat our component hierarchy as fully dynamic and controllable object. You cannot code a serious fully declarative app without this feature.

There is a killer feature of vDOM that Svelte has nothing to replace with. It is the ability to treat component hierarchy as an object.