Yes, but you can suppress a trench with mortars and do a combined arms attack against it. As for Tanks, there's other munitions better suited, the only reason the UAF aren't use them is scarcity.
When scarce weapons can defeat abundant weapons, and it's not because of range, it's usually because of precision. Drones are great at precision. 3 mortar rounds falling within 30 meters of your target trench are still ten times less deadly than a single FPV drone you can pilot straight into it.