At what specific point does using setState genuinely become sufficient for a genuinely simple Flutter app, and when does a genuinely more particular dedicated external state management solution actually genuinely become worth adopting instead?

setState is genuinely perfectly sufficient and quite appropriate for managing state that genuinely only matters to just one single specific widget, such as whether a particular expandable section is currently open or closed, or the current text within one single specific text field, and a genuinely more dedicated external state management solution such as Provider or Riverpod generally becomes worth adopting once you genuinely need to properly share a given piece of state across several genuinely separate different widgets that are not directly related to one another through a simple parent child relationship, since setState alone would otherwise require you to manually and quite awkwardly pass that same shared data down through several genuinely unrelated intermediate widget constructors.

// setState is genuinely fine for local, widget-specific state
bool _isExpanded = false;