Total control for maximum performance is not synonym of inconvenience. There is a lot of cameras much easier to master. Are they less efficient? Certainly not or Leica would has stick with the Barnack concept until now. Even manufacturers which copied the Barnack concept switched to something else after a decade or two, not without reason.
SM Leica cameras are small, aesthetic, silent but no magic. They can be effective but I don't consider them as the most versatile. For that, SLR are way ahead.