Even if the goal was to showcase what can be done in JavaScript now, it's a rudimentary isometric visualization of animated sprites with very simple game logic (not even basic path finding).
Just to make it clear, regarding the creator and the project:
* Is there something bad with him creating something? No, not at all. Cudos to him for making something! Especially for making it open source. Let's anyone peek at how he has done what he has. Sweet.
* Is there something bad with with how he is doing it? Yes, he is using copyrighted graphics he doesn't own the rights to use.
Regarding this as HN:
* Is this technically interesting? No, not even remotely. Throwing graphics on a canvas and point-and-click basic game logic is not interesting. Point out to me a basic mechanic or implementation that isn't trivial (overlay of minimap is the most interesting thing that comes to mind).
* Is this aesthetically interesting? It would be, if it was original art. Seeing as it is just "borrowed" sprites, the optimal goal would be a screenshot of Diablo 2.
* Is the title accurate? No, not even remotely (there is much more to Diablo than sprites).
* Is the project anywhere finished and presentable? Maybe this just personal preference, but I don't like seeing other people's pre-alpha demos.
tl;dr: Stop wasting people's time with technically uninteresting posts with misleading titles alluding to the contrary, to projects using assets they shouldn't.