The lack of easy browsing is an issue, but Darktable has never purported to provide an image browser / organizer. Quite the contrary, the devs have always been crystal clear that they hate the concept with a fiery passion.
The lack of good open-source image browsers has, oddly enough, become a major problem. Only recently did someone float a pretty good one for Mac (FlowVision). I don't know what options there are on other OSes at the moment.