Yours is real fast when apps are loading and you get a spinning wheel for 15 seconds beforehand? I think you have ATV3 Stockholm syndrome my fellow man.
The benefit of an ATV4 and ATV5 (4K) is they offer an app store.
Imagine an iPhone without an app store. If you are happy with the apps that come on it and don't need or want more apps then you probably wont benefit much from updating, just keep your ATV3 and be happy.
I would mention the benefits like HomeKit automation however I have a feeling you "don't need no automation".