The GR III was always going to be a tricky release for Ricoh to pull off. The GR II was so well-loved that a rushed or poorly thought-out successor might have seriously upset a core of loyal users that Ricoh can ill-afford to lose.
Street shooting and casual photography; or travel photography where a small and light camera; with a medium-wide lens is very useful
Any work that requires long shooting sessions; long focal lengths; or low light shooting; where the GR III's autofocus system can struggle