How should our community treat out-of-date and abandoned Apps?

Sometimes a dev is away for an extended period of time, then returns to development. Sometimes an app is officially abandoned but still functions well. Sometimes an app may be under active development but not yet compatible with the latest version of Lemmy.

Should these apps be excluded from our Apps list? Which ones? What criteria should we use? Should we maintain a list of “Old Apps” for posterity, as a code database, etc?