For a cutting, the stem needs to be physically strong to stand up by itself in the rooting medium, after being pushed or dibbed into a hole etc.
The leaves need to be hardened enough to keep their shape and not droop, or not too much. If you are pruning fresh cuttings and they basically wilt straight away they are too soft. They probably need to be able to retain their shape for a while after cutting to succeed.
You might get away with softer stuff under extra care or mist systems.