A courtmartial would have resulted in jail time.
Then 1/4 of the crew would have had to have been devoted to maintaining the efficiency of their incarceration.
It's unethical to abuse prison labour, but it's fine to get these people to hold up to honouring their legally binding oath of duty.
Janeway was less interested in dealing with a guilty verdict than the Maquis or the Equinox 5 were eger to be found legally accountable for their horrific crimes.
It's how Wall Street didn't get blamed for destroying the world a couple years back.