If we don't sin, Did Jesus die for nothing? [Spirituality & Religion]

No. You have sin as part of your nature.

For all have sinned, and fallen short of the glory of God. Romans 3:23

Read 1 John 1:8-10

You're right. The whole Christian teaching hinges on first buying into into 'original sin'and a list of wrongs we might additionally commit. There's no reason to think it rational.

This is what I'm sayin'. We should make sure He dies for something, right? Let's do our parts!

If you commit sin you are then made to be born as cactus or crows or maybe mad dog

No because he died for our sins

That's what the devil is for.