The "Non-Incremental" ERC Challenge

A prevailing comment responsible for the failure of many ERC AdG (Advanced) applications (though also found in Starting and Consolidator grants) pertains to the ‘incremental nature’ of the proposed research. Why is that? How can one successfully design a project which reflects the naturally occurring progress forward which builds on past achievements, current knowledge, expertise, and preliminary results, while at the same time conforming to the  ‘non-incremental’ ERC unofficial requirement?