You Shall Not Climb!
You Shall Not Climb! (YSNC) is a server-side Fabric mod that removes the ability to climb ladders from mobs that shouldn't have this capability by design.
The bug report MC-148545 "Mobs can climb ladders" was marked by Mojang developers as "Works As Intended".

Obviously, this makes no sense since it's intended that most mobs don't deliberately use ladders. This seems more like a side effect that is actually easy to fix, which is what this mod does.
Frequently Asked Questions
Which mobs can no longer climb ladders?
List of mobs that cannot climb ladders:
Allay, Armadillo, Axolotl, Bat, Bee, Blaze, Breeze, Camel, Cat, Chicken, Cod, Cow, Creeper, Dolphin, Donkey, Elder Guardian, Ender Dragon, Endermite, Fox, Frog, Ghast, Goat, Glow Squid, Guardian, Hoglin, Horse, Llama, Magma Cube, Mooshroom, Mule, Ocelot, Panda, Parrot, Phantom, Pig, Polar Bear, Pufferfish, Rabbit, Ravager, Salmon, Sheep, Skeleton Horse, Shulker, Silverfish, Slime, Sniffer, Snow Golem, Squid, Strider, Tadpole, Trader Llama, Tropical Fish, Turtle, Vex, Wither, Wolf, Zoglin.
Do I need to install this mod on the client?
No, it's only required on the server.
Is this mod compatible with mod "X"?
Maybe. YSNC provides an entity type tag "ynsc:cant_climb_ladders" for compatibility with other mods. If your favorite mod contains some mobs that shouldn't climb ladders — ask the developers to add support.
Will there be support for older versions?
There are no plans to backport to previous versions.
Credits
- SyberiaK — mod author
- DeDiamondPro — came up with an excellent name for the mod that many people liked:
