I think it's worth to check the workflow video[1], how it is to actually build those animations. It really surprised me positively!
[1] https://vimeo.com/185587462
The best part is they don't try to do too much. Since you invoke them via code, not some all-in-one editor, that makes it much easier to go back to your code when you're done. I feel like that transition is most of the problem when dealing with other tooling (see Photoshop's "copy layer style as CSS").
So the idea was: you have your page -> you add debugging tools -> craft your animations -> remove the tools and animation still there.
Also, since project's resources are limited - we had to make those simple tools and then connect them to something more matured like https://github.com/legomushroom/mojs-timeline-editor (which is in the process right now). This way we are able to release MVP early and get feedback early while constantly improving the tools.