The mod specifies "minecraft": "1.17.x" instead of "minecraft": ">=1.17", so it crashes in Minecraft 1.18.

https://github.com/CaelTheColher/Capes/blob/master/src/main/resources/fabric.mod.json#L40

Specifying >=Current allows the mod to potentially function if later versions of Minecraft without any changes if a version happen to not break the mod.

At the moment, it's not possible for normal users to test if this version is compatible with 1.18.

The version happened to break the mod, this is why its specified what version the mod is guaranteed to work in.