You're not alone in those thoughts.
The consensus that I've received about "where did people go?", even outside this forum post, has been lack of active development in WvW.
An active development cycle would have added so much more to this game mode over 10 years. Strikes, new zones/stories, raids, etc. have taken their dev time and WvW has always lingered. This is why competition is important. Maybe other games will look into RvR and force ANets hand.