I’m not sure if this has been suggested before, if it has I’m sorry but it’s pretty much what the title says, the ability to drag monsters towards a zone you want to attack in the battle phase.
Dragging is imprecise when you have a field of 7 specific zones your opponent could occupy. Duel Links can get away with it as you only have 3 zones to attack. By comparison, you have less than half the screen space to space out each zone.
The lack of dragging prevents misclicks and misinterpreting actions when on mobile.