The only thing I do on a treadmill is aggressive hill work, the minimum gradient I use is 3% and can happily go up to 20% on mine.
Currently, its very difficult to get to the climbs as a runner. I have to cover a pretty long distance just to get to them, on a bike its not a big deal because I get a 10-15 minute warm up before the work starts. Running there would take an awful long time when Im looking for a hill workout.
Of course I can just run with the incline settings to my personal preference, but why am I on zwift? Id love to run/hike up Epic KOM or Alpe du Zwift (once I unlock it). Anyone who has ever trained for an ultra marathon knows there are climbs like that and worse. Anyone else feeling Zwift’s current iteration is too flat as a runner?