If the rules themselves have utility, don't throw them out. Being under a new covenant, with a faith based get out of jail free card that allows you to throw away laws that have no utility in today's age, does not mean that you shouldn't pay attention to good lessons.
There are prescriptions for everything in there. If you let your fields lay fallow every seventh year to rejuvenate the soil, is that a good thing, or do you stop doing it because you don't have to anymore to gain salvation...?
The new covenant is supposed to fulfill the old, and transfer your salvation to grace. The counter would be 'just because we have a new covenant, do we throw out all good from the old covenant?'