After complaining, the Israelites received the death penalty. Is that fair? It seem to be a touch heavy-handed, but there is more more to the story.
Most of ancient Israel, because of their hardened hearts, did not please God. We must reflect on the the ways they stumbled so we can walk differently.
If we, like Israel of old, choose to sin, we will receive the same consequence. Two thirds of the book of Numbers emphasizes that if we sin, we die.