That's a bit of an understatement

. Because arty have indirect fire and range 3, they can just clear a path in front of them and advance 1 row whenever it is clear(ed). Especially on rough terrain it is difficult to flank them, and their disability to move+shoot is shared by normal units. A cavalry needing to cross 3 hills before attacking an artillery will feel like a GWI with Haig breathing down his neck. This is of course compounded if the attack is from (citadel-captured) friendly territory.
If you have equal firepower and no airpower is in play, you will probably get
a proper WWI style standstill at distance 4, and whoever moves first is blasted to pieces, but I've not actually seen that happen.