No its not. Slicer software is just CAM software for 3d printers. It just creates Gcode like any other CAM software. Calling it " basically just your interface to the dials and knobs on the CNC settings for speeds and feeds." shows a deep misunderstanding of operating CNC's in general.
Your manual controls on pretty much all 3d printers suck. But that's because manual operation is considerable far down the priority list. I've never seen one that did jogging other than setting an increment and tapping a touchscreen button to make it move 1 increment.
Every CNC machine I have ever ran did way better with the jogging. Even the ones from the 70's. You set a speed with a knob and then hold down a button. It goes till you let up. Or you use a rotary wheel for fine control.
And don't even get me started on homing. The homing sequence on all the printers I have dealt with is home X and Y before homing Z. Most machinists will be aghast at this as if you are homing all 3 axis's at once you home Z first to get the tool out of the way.
While you are technically correct in that DigDug used the wrong analogy, they are correct in that slicers are really good now and you won't spend hours dialing in temps, flow rates, and speeds like you once did. You do simple CAD stuff (e.g. scaling and orientation), add supports if necessary (and the auto option usually does a good job), then press slice to get a gcode file which you send to the printer (either network, serial, or through a SD card).
Regarding Z-homing being last - usually endstop positions are on Z-, not Z+, so they do a bit of a hop (2-10mm upwards Z) before the X and Y homing so they don't crash the head. If your Z endstop is on Z-, you can home that first since you know the head is out of the way.
EDIT: to be specific, this is for "bed-slinger" printers, but the concept is the same for fixed height tool head printers (eg where the bed is what's raised and lowered).