Really the only way to lower the file size and there for load time of your animation is to alter the amount of content or when exporting the file, to lower the quality of your animation.
This is something however, you and or many others, do not want to do.
If you still want to go ahead and use the large file I can only suggest writing into your animation a 'preloader' if you haven;t done already.
This means that although the file is big, it loads before playing. This will show visitors that it is a big file but once it is loaded fully it will play. You can find many tutorials on the internet.