How do you motivate a conscript? When I was in the British Army, which is volunteer only, commanding a basic training troop if someone was wanted to give up we could say to them 'if this isn't for you then you can go home' (of course we did coach and mentor people to help them, I mean in cases where people just give up and stop soldiering when an exercise gets tough). They usually worked extremely hard to get into th…
On the other hand, the professional army in Sweden is largely recruited out of the conscripted soldiers, and unless it's propaganda they are considered to be professional and reliable, for instance in recent missions in Afghanistan etc.
It was a long time ago 99% of the men where forced to do their military service. The idea is that you are forced to at least go through a recruitment process and/or a short introductory education, you can swoop up those that are talented but uninterested initially, but might reconsider.
I think you are right in that if you can't attract motivated and talented people, you should fix that rather than force people.
In my own case, the idea of mandatory training did more harm than good as it just pissed me off on principle... I got drafted to a probably quite interesting service actually - that I likely would not have appreciated. But as the Soviet union just had collapsed, someone decided that they could spend the money on something else before I actually started, so I did never find out.