Personally, guiding junior teammates down the path away from purely "Writer of Code" to "Implementer of Functionality" has been working well for me.

If you get them involved in the design process, they feel heard. Feeling heard is one surefire way to have a person feel involved. Feeling involved fosters a sense of ownership and pride which in turn helps keep a person engaged.

Yeah I like that, there’s probably something to this full stack builder persona that could keep people motivated long term. So long as they feel ownership, seems like that’s a pretty good bet for long term engagement

Management 101.