In reply to Kristin.

@Kristin A reason why we've been focused on the customizer first before front-end editing is due to compatibility issues across themes which make a general purpose plugin for frontend-editing any theme very challenging. The customizer was designed for theme compatibility which is partly why the controls do not appear inline. Nevertheless, the work being done in the customizer is laying a foundation for bringing editing to the frontend. For more information, see: https://wptavern.com/customize-posts-plugin-and-selective-refresh-are-paving-the-way-for-front-end-editing-powered-by-the-customizer#comment-170084