Very true. It would be the job of the implementors to provide new properties that handle common use cases. For this example in particular, we now have:
The problem is that right now implementors are all building different browsers that are attempting to provide a single consistent implementation of features as read off a spec document. A daunting, unenviable task to be sure.
Perhaps the solution is in frameworks or abstractions but that is also troubling. Who knows, it's still the best we've got right now, and that's going to have to be good enough for me.
animation-fill-mode