Darktable's targets digital photography enthusiasts or professionals. The learning curve is steep. Picasa's target demographic was "everyone". So probably Digikam.
I can confirm. Every now and then I want to edit some of my photos and run Darktable, only then to remember it has zero automation and a hundred of sliders for individual adjustments. It definitely requires dedication to use, more of that than I have to give for holiday photo editing.
You can get by using the same 5 sliders for almost all your photos. The other sliders remain available for edge cases or when you want to go the extra mile.
