Ok 'structurelessness' is another word for chaotic (or worse, secret structure). But there are many alternatives to simply 'layering' where you progress from one title to another, always 'upward' whatever that means.

Having roles, being structured, doesn't mean layering and promotion. It means clearly defined jobs and roles that encompass sets of jobs. You can still be 'unstructured' if that means no simple hierarchy. Instead folks can all be responsible for their tasks, empowering folks to do the right thing without a 'boss' to enforce it.