though that might be true in principle from what I've seen so far it looks like the ECS's (or at the very least ECS systems made in Rust) really like knowing the types they need to work with due to pretty heavy use of generics. Which is not the case when mods are involved I would also argue that in Java and .NET world people can probably just replace the entire ECS system for as long as the API stays compatible in some way, shape or form (based on seeing what people did with Minecraft Java)