Why couldn't we reconcile ourselves to God?

I always hear people say things like, 'the debt was too large' ... well, why? Why couldn't I pay for my own sin? I don't like that Jesus took punishment for me, I would hate for my earthly father to get fined or beaten or imprisoned for me, it would enrage me, it's completely unfair. I want to pay the price myself. Why can't I? The only thing that seems to make sense is that for some reason there had to be a blood sacrfice and that sacrfice had to be a perfect being (similar to how animals could not be sacrficed if they had any defects.) ... but why? Why does the person/animal dying need to be perfect? It doesn't make sense to me yet, I know it's the truth because I believe in God but I feel like there's a block in my understanding, like I'm waiting for a lightbulb moment where I go 'ahhhh ok now I get it.' PLEASE DON'T SAY 'there are some things we will never understand because God is God and mysterious and we just have to deal with that.' I don't believe that is the case with such a critically important issue. The early Christians seemed to have such a good grasp on the whole concept but it's evading me. Please offer your understanding if you get it. Please don't say anything if you're not 100% sure. Thank you so much, I really want to get this so I can move forward in my faith.