InDesign began exporting EPUB with CS4, as I recall, but it was little used. There were minor changes in CS5. Beginning in CS5.5 and CS6, the entire export engine was rewritten and extensively changed and the code got much better and more refined. I expect this will continue in future versions.
The CSS code generated by InDesign will be verbose as all machine-generated code is. However, in later versions of InDesign, you can create your own CSS file and use it. That's probably the recommended thing to do. Or, you can edit out the "useless data" in the InDesign-created code.