Probably the thing to do there is to keep the click+drag anything-anywhere cable interface, but make it much cleaner, simpler, more modern and faster to navigate.
More diagram-like.
Alt-click on a connection to fly you directly to the other end of the cable.
Hover over a connection to show a pop-up tool-tip with the name of the device+connection at the other end.
Dragging a cable zooms out to a more global rack overview where devices are highlighted as you hover the cable connection over them. Lingering within any device zooms back in to the standard rack size so you can make the final connection.
Press a button or hit a keyboard shortcut to zoom out to the same rack overview any time; click on any device to hide all connections but the ones made with that device. Press K to toggle show/hide all connections.
When dragging or shift-dragging a device, use icons to clearly show the routing that will result from this action.
All that kind of thing. Simple, obvious stuff.
Navigation and workflow and general appearance of the rack could be massively improved and modernised, but as a GUI the principle is still totally sound. It's just that the execution is tired.