Ton Roosendaal, Blender's creator, has been pushing for it to become more of a platform. His vision is for there to be an entire ecosystem of Blender-based apps with individual purposes and UIs, all developed on top of it, and I'm pretty sure the Extension Platform is the start of that.
...but this also starts to solve a lot of the maintenance and discoverability issues that have hung around add-ons for their lifetime. Many people don't know they're there at all. People argue several should be standard parts of Blender (Node Wrangler, notably).
Making a Blender-based app that's a fake Adobe After Effects, most of the power is there all ready. Just having a 2d scene that's more than grease pencil, matte video without going to a seperate window, nesting comps, able to drag things around by eye instead of sliders, etc. It would by amazing.