It can be, it depends on the company and what you've done in the past. Design is not required for ESEF compliance, however, it does not mean that you have to change your process if you've created a designed report in the past. Check out Jackie Whitworth's blog discussing design under the ESEF mandate for more information.

To understand more about the ICML Exporter, watch the video on Moving Workiva Content to InDesign for Design Reporting.