I can’t say much about Impact, either. As far as I remember, it resembled Arcade but supported slopes in tilemaps using a proprietary tilemap format.
As the changelog says, the light pipeline was deprecated because it was unfinished. The forward renderer has unexpected behavior, while the deferred renderer simply just isn’t there (there’s a shader for it, but it doesn’t look like it implements deferred rendering at all). This alone limits the usefulness of the pipeline, as forward rendering really isn’t the best option if you want many lights. In my opinion, proper lighting is too specific for a 2D framework and it’s often easier to fake it with overlays and masks.
If you really do need real lights and you know how the WebGL pipeline works, look up a tutorial on lighting with WebGL. I doubt you’d find anything for 2D lights, but even a 3D system shouldn’t be too different.