I mean you can look at Russia as an example for how much of the economy was hurt by forcing people out of normal occupation and into service. You also have too look at their abysmal attrition rate to see its unsubstainable and if used primarily leads to worse and worse outcomes on the battle field as they less and less qualified personnel.

Appealing to morality is probably a lost cause for someone supporting a draft, they have already bought into war as a solution. Like moral arguments that Russia is choosing to sacrifice millions and set back their region is something they are already choosing to ignore, forcing people to do it minor in comparison.