Letting the LLM generate use cases is probably not a good idea. But writing common use cases and having a bot crawl your app and then write up how many steps it took to accomplish the goal is a good idea that I hadn't thought of before. You could even set it up as a CI check to make sure that new features that introduce more steps for specific flows are very conscious decisions. In a large application this could be a very useful feature.
The author creates art using their own custom library that uses CSS-like syntax to render HTML, SVG, and more recently shaders. The point isn't that this is the best way to do it. It's simply a trick that the author used to do something with their own bespoke library that they were trying to do.
GSAP is a bit more robust than anime.js. Over the years anime has been adding more functionality and changing its syntax to be more like GSAP's. They're both solid libraries though