I get that its artificial in its way, but I figure it'll never really last so I guess it doesn't bother me as much. Sometimes figuring a way to work around something can be unexpectedly inspiring. It certainly was the last time they did more than one series of no-old Villains period, the show had a pretty good track record - series 13, 14, 15, and 16 have a number of important episodes that introduce concepts that became cornerstones to later series.