It is more of an adjective to describe a task. "This homework was long and laborious" You can just say a person is hardwork if they like to work.

If you said someone was laborious, that would (if anything) mean that they were hard work to listen to. In other words, they laboured over their words, talked in a monotone, and repeated themselves

Labourious is used to describe job or way of doing something that is often boring, long or difficult.