It may seem harsh that one who cursed God would be killed as punishment. However, recall that God is merciful to give us a way out of sin’s punishment at all; He doesn’t have to extend mercy for any violation of the Law. That He doesn’t extend mercy for violating this requirement should signal to us that it is very important to Him.
You may not curse Him, but do you consider Him less than how He presents Himself in Scripture? That demonstrates a lack of reverence for Him like the cursing demonstrated. Since God has preserved this account for us we need to use the opportunity the story gives us to assess our own condition.
The Law’s provisions for Sabbath and Year of Jubilee teach that the land and the wealth it produced did not belong to the people but to God. He has reasons for His requirements that are beyond our ability to comprehend, but we can discern why these requirements make sense despite the world’s calling them crazy. His people’s observance of them would curb materialistic values and build their trust in God. How do these principles apply to you? Do you demonstrate devotion for Him in the way you carry them out?