more modern animation options, or more possibilities of customization.
Keynote has a great feature that creates a transition between two slides transforming the text from one to another. this would be great.
Many animation options feel quite outdated (such as bounce, boomerang, credits, swivel), they should be completely revamped asap.
Other animation options (such as zoom in/out, peek in, strips, wipe) should be possible to happen at any angle, not only up/down/left/right. They also should have a smooth start/end/bounce end option just as many of the other ones. Especially the zoom, it's so linear I prefer to use it alongside grow/shrink, but of course this is far from being the ideal solution