Before I address the post in general, I would first respond to that claim that the two great commandments are not part of the ten commandments. They are, for the ten are based on loving Yahweh God with all our being and loving our fellow humans as ourselves, and even loving fellow creatures.
The new covenant is available and we who are believers, in Christ, are included in it. The law written on our hearts is not instantaneous with that, but develops, with ultimately being complete in our hearts. You as others were likely never going to kill another human being anyway, even when apart from Christ. But in Christ we are to grow, and see wider application with what is commanded. You will learn more for that, as I will too, and we will come to live it from the heart, when all is fulfilled. And indeed the morality doesn't change, and continues. You think rest with observing Sabbath is not involving morality at all, it is just ceremonial? It is holy, as Scripture shows, it is also made for man. It was wrong for having others work for one, this applied even for animals that were put to work, all were given the day for rest. So gentiles are excluded? Or because of any being Christian they are excluded? It is still wrong to tell others, the day of rest is not for them. If you have others work for you on the day of rest it is wrong. There is morality involved in this.
Yes, ceremonial things were shadows of what has since been fulfilled. No priestly actions are needed now, apart from Christ who is our high priest. And no animals have to die for us anymore.
The covenant was based on what blood was shed. So with the same commandments in the law, there were different covenants, the old with sacrifices that Levitical priests took part in, and the new covenant with Christ fulfilling all requirements for that, which was of same law.
You are right that obedience is not just incidental. Many people don't murder other people. But see what I just wrote above regarding this. You must love others, in the way you would only in Christ, and if you hate any, you don't fulfill it and are contrary to the commandments. In the same way loving Yahweh and other humans, and being loving otherwise, will lead to doing such things. Don't just claim your love is perfect and you don't need to learn and grow to do more.