No it shouldn't be. Although voting is crucial. Mandatory voting is an overreach of power. At least in the United States it would also be unconstitutional because it derives its consent from the governed. If you force people to do anything you do more harm then good. This is the argument made for forcing alcoholics into treatment it won't work unless they want it to. Someone could purposefully vote write in and say smth random. What would you do if someone doesn't vote? Would you throw them in jail. Because there are so many people that won't vote. It would overburden the criminal justice system with people who simply forgot, people who literally have dementia, people who are confined to a hospital bed. The enforcement alone would cost millions. The U.S. criminal justice system is already over worked and over taxed spending millions to keep each prisoner there. Fining people would be equally harmful, some people who don't vote might not because of poverty and mental illness. Fining them would worsen their lives. Ultimately this would be a dictatorship. Campaigns to increase voluntary voter participation would be far more effective. Mandatory would just build resentment.

Well the people who show up show up because they care. If they don't show up they don't care enough to. Why should politicians focus on people who don't care.

Forcing people is bad. Jury duty is mandatory but that is because if they didn't have it no one would participate. If you make everyone vote some people won't know anything and might vote randomly. Ultimately people haven't been forced to vote, they've been forced to do jury duty. If they're required to vote it will cause an uproar.