Let’s come up with new “war machines.”

Yeah! Large animal corpses (cows, for example :D), and have the plague trigger in a certain radius with every corpse!:D :D :D

yeah I've already seen that :D maybe just throw your own monsters in there so you don't even need to break the gates:D
The ram is unnecessary, it's true, they aren't heroes anymore. Better, for example (off the top of my head), a magical catapult throwing magnetic magic spheres that explode on impact and break the chains and locks holding the door, or simply a road teleport to teleport a unit behind the fence. And elves, as I already mentioned regarding the "super dendroid," could entangle walls and the moat with roots or vines from underground; and when defending, conversely, hold up a breaking wall or door.