Unity has a ton of extra layers since they are trying to support a mixed game world with both game objects and entities. In order to make a entity from a game object, you have to bake the game objects using something called "authoring". You also can't debug any of the entity stuff visually, only using some tools that display information about the current world state and number of entities. You can't click on entities to drag them around or inspect them.

In Murder, the editor lets you set up your sprite with hit boxes and entity components similar to working with Unity prefabs, but you can just drag those into the game world "scene" and they are already entities ready to go. Any systems will include the entities that it filters for without any additional steps. All you need to do is write the scripts for the components and systems, then add the component onto an entity into the world and add the system to the list of systems running in the world. Not to mention doing all that dynamically with support for more complex implementations.

TLDR; ECS in Murder is just regular C# with some different context. Learning ECS and using it in Unity was like a whole other world even for an experienced Unity programmer.