The French version is just a voluntary, month-long thing. Countries are full of volunteering opportunities. You can join the armed forces cadets if you want the military, there are charities, volunteering in healthcare, Duke of Edinburgh scheme, etc. in a Summer holiday. That sort of thing is a pointless government programme that exists for show not effect.Several countries in Europe have some form of national service already, either militarially like Sweden and Switzerland or community based like France. I do not see why it is such a big issue.
If you want to properly shove someone into service, it needs to be proper service. And then all the problems above exist. It actually makes most sense in terms of defence, in terms of ensuring there are reservists with some hint of military experience - although even that is pretty marginal. A 30-year-old who did national service for a year when they are 18 will have forgotten pretty much everything useful except the very basics and some general principles, so effectively everything would need to be re-taught if they needed to be called-up. This is why many countries have reservist programs instead. If you've got sort of "part-timers" who do a bit of training and practice throughout the year alongside the regulars to keep things fresh, it's probably much more effective.