It's a draft, as long as the service is not voluntary.
That's not necessarily a bad thing. Militia service was once manaddorty. In fact something like a widespread militia, with the active force and something like the current reserve and guard recruited from that militia. It would consist of some basic training, and then fairly infrequent refresher training. No technical training, other than that required to operate the most basic systems: assault rifles, grenade launchers, maybe up to something like Javelin antitank and stinger anti-air systems. It works for the Swiss, although we'd have to recruit many more of these militiamen to active service.
Of course that would all cost money, money that the Dems would rather give away, and that the Repubs would just as soon not spend at all.
But this is NOT military service. Military service is to defend the people with an appropriate use of physical force against enemies, or a threat of same. Given a sufficiently grave peril, one could certainly justify a military draft, and it would be temporary, lapsing when the need was gone. You cannot compare civilian community service. The streets always need cleaning; does that mean we should have a permanent draft of citizens into involuntary service cleaning the streets?