A few observations. I’ve recently begun listening to a pastor who approaches the New Testament in what to me is a more logical way. I’m not totally sold on it, but it cleared up a lot of contradictions I’ve continued to encounter in over 20 years of involvement with evangelical Christianity. The big problem churches have is they are often preaching the wrong gospel. Not an unbiblical one, but just the wrong one. Paul’s gospel is the only gospel that is relevant to us as the church. That is the gospel of grace and liberty, not enslavement to a new law. What we call “the gospels” of Jesus are pre-cross teachings to Jews under the Torah. There is still a lot of conditionality in Jesus’ teaching — “judge not, lest ye be judged,” “forgive us our debts as we forgive our debtors,” “you will know them by their fruits.” Churches that focus on those gospels tend to be more legalistic. It sounds like your early church experiences were with churches that focused on the wrong gospel. Those churches often blow up spectacularly in pastoral scandal.
Now, you say that Christ taught that we should transform the earth, bringing the Kingdom of Heaven into reality. Historically, the church has tried doing this and our world is still a mess. This was a very popular sentiment toward the end of 19th century in America and Europe. Some of the foundations of socialism are in this Kingdom-creation idea. Jews have a similar “fixing up the world” idea. If we could just redeem the world system for Christ, then He would return and establish His rule forever. World War I blew that positive, progressive idea to Kingdom Come. This was not what the church was meant to do. The church was meant to take the gospel of grace as revealed by Christ to Paul to the ends of the earth. Paul says that this world system is governed by demonic powers. We as individuals must be transformed by the renewing of our minds through the Word of God, but the world system itself is irredeemable. Governments and ideologies will come and go, but the gospel of grace will be preached until Christ returns for His church. Where that gospel goes, personal restoration follows, but it’s not something that really grows upscale. The Roman Empire became heavily populated with Christians, but in the end, it collapsed and a corrupted “Christian” structure existed in its place for the next thousand years. Christians probably thought they had finally brought about the Kingdom of God in the Holy Roman Empire, but that didn’t turn out to be true. First class, wrong flight. Following the wrong gospel or having the wrong goal inevitably leads to disillusionment.