Not been to Krka, but Plitvice is special. The problem is the hoards of tourists on buses that arrive each day from the coastal resorts - a bit like cruise ships that spoil places for everybody. Take them out of the equation and it’s a much nicer place to visit. There are two solutions…visit after mid afternoon when they’re off back to their hotels or arrive early and do the trails in reverse. Shooting them would be a better solution but might get you into trouble?