Do All Themes Have The Editor Function?

I cannot see the Editor function under Appearance, but I’m running my sites in a multi-site environment, so this is to be expected. However, I’ve been told that some themes don’t have the Editor function at all, even in a single instance. Is this true? I’m using the Liva theme (which is no longer supported so I can’t ask them).

I’m just trying to find out if I don’t have access to the Editor because of the multi-site environment, or if I wouldn’t have it even if I were in a single instance.

Thanks!