I gave Stage Manager a fair shake for a few days when I first installed Ventura, but even after a few days I was damned if I could work out what the point of it was. It wasn’t better in any way I could see than just fullscreening apps, or having task-related apps on a new virtual desktop.
The only thing I could say for it is that if you’re coming to macOS from iPad, there’s a systemic familiarity to help you transition.
But otherwise all I can say is that at least it’s optional.