The answer to why we’re not perfect like God is simple - because we chose not to be.
According to the Genesis narrative, when God made man He made him (man and woman) perfect and innocent. Unfortunately, it wasn’t enough for them simply to be made in God’s image; no, they wanted to BE God. Therefore, they disobeyed God (the forbidden fruit). In doing so, they lost their perfection – their “innocence”. Racked with guilt, they hid from God (much like a little child covering its eyes and proclaiming, “You can’t see me”). Genesis chapter 3 tells of the consequences of their actions – as well as the beginning of God’s plan to return man to that perfect state once again (through Jesus). Even today, mankind still wants to BE God. Since they can’t be, they try to make God in their image -imperfect.
God is perfect in that He lacks nothing and in Him is nothing lacking (He’s absolute). Man is imperfect in that he lacks the ability to get himself back to that perfect state he once had. To this day man (humans) refuses to admit that he’s the one to blame for his predicament (his problems). Instead, man blames God. Man even goes as far as denying God’s existence, while still maintaining that his problems are God’s fault. God desires for us to be perfect. In fact, He paid every price and jumped every hurdle for us, just so we could be perfect once again. Yet we refuse Him, choosing rather to relish in our imperfection and misery.