I hear that. I have a hard time dividing the disciplines by the intensity of the demand as they are all probably more than I can fathom.
They all have differing demand mixes of quickness, agility, power, precision and speed.
Think of this as a linear spectrum for the basic shared attributes of the 4 disciplines:
quickness - agility - power - precision - speed
You can base this spectrum off of the actual measurements involved such as speed, radius, G force obtained, number of gates and lateral/longitudinal distance between gates.
All four disciplines require all five of these attributes but in different mixes. Where SL is on the quickness end of the spectrum, DH is on the speed end of the spectrum. As well, you will find GS just left of center and SG between GS and DH.
So, as you might surmise, GS may be considered to, at least mathematically, have a more balanced blend of required attributes.
That said, I, personally am just about equally amazed by all the WC disciplines (including the combined not listed above for practical purposes) none having more or less value than the other.
I think a skier is going to be more drawn to the discipline that contain the most of an individual‘s most appreciable attributes.