No, it is forced labor and indeed a serious infraction on human rights, but it's by no means slavery. Slaves can be sold and subjected to a bunch of other abuses.

Unlike slavery forced labor can be acceptable in certain conditions. I don't think conscription in Western countries falls under that. It's far too expensive (delaying people's entry to the workforce by a year should cost more than 2% of GDP and you can buy a lot of advanced weaponry with that much money) and in most places getting enough people into the military should be doable by offering more benefits. But in countries like Ukraine or in the West when we're talking about things like natuaral disasters it may be necessary to force people to work for the community.