The reason we have compulsory military training is because of our lovely neighbours, and I don't mean Sweden or Norway. We need some level of defensive force.
It's a good experience too where you'll likely learn new skills and discipline, bond with others, stuff like that. When I did my 9 months we had guys who lived in Spain and Australia. Their mothers were Finnish, they barely spoke the language but they volunteered to come and didn't regret it.
The fellow from Brisbane had it rough at first. In January it was -25C outside and we spent two nights outside. In the silent and dark forest you only heard jos teeth chattering lol. Think he did the old trick of eating tobacco so he'd get a fever and got to hospital.
Anyway, civil service is also a good option, not everyone can do military service. But in a country where education, healthcare etc are free and we have a good social security system, 6-12 months of you life for your country isn't too much to ask imo.
Many people against compulsory military service are those who don't feel like working or doing much of anything, but they're always asking everything for free anyway. Wankers.