I haven't thought about it, but I'm open to the idea. What kind of animation engines do you have in mind?

Yes, the absence of 3D is very much a choice. I believe this need is already covered pretty well by existing libraries like three.js and threlte etc. These are relatively large and complex to use, because you essentially have to adopt the mental model of having a whole 3D scene or something like that. With Svader, the mental model is just that you have a canvas with an attached fragment shader, which paints the canvas with respect to some input parameters.