I'm sure I've seen video of oranges being harvested mechanically. I'm sure it can be done but probably not economically everywhere especially if the terrain is difficult. For mechanical olive harvesting see: https://ilcircolo.eu/olive-harvesting-by-hand-or-with-machin...

Orange farms are on flat land and all the trees are on a grid and trimmed to exact sizes

That may be true of modern farms elsewhere but is not the case for historical groves here. They are sometimes spaced appropriately but that's about it. Usually on vehicular-inaccessible mountainside terraces.