There has been people that all lived under one religion. I like using the example of the Aztec religion. It kept their society and culture going for centuries. Then the Spanish conquered them and outlawed their religion and forced them to believe in a Trinitarian God. Was that "renewal" better? In a way, better than a religion that included human sacrificing. But was this new religion true? Not by Baha'i standards.
But that same religion, the Catholic Church, had great power. And replaced several other religions that had their own Gods. Then the Protestant Reformation... a "renewal". Was it true? No, not by Baha'i standards, because they still had sin being inherited from Adam, Jesus as the only way, that they were the only "true" religion, and that God was still, the Father, Son, and Holy Spirit.
But when you say the "current" system, it's kind of secular isn't it? We are moving away from allowing religion to have too much power. Why? Because religion was the problem. And now you want to replace the "current" secular system with "God's" laws and government? It might be better. It might be exactly what is needed, but how many people are going to trust a religion to run things?
But then Baha'is say, "Not to worry, the laws are only for Baha'is." I don't think so. It sure seems that the Baha'i Faith is setting itself up to be the governing body for the whole planet. The Local and National Houses of Justice and the Universal House of Justice. And if not, then do you really think a secular world government isn't going to get corrupted? Look at the U.S., we don't even trust each other and our "democratic" elections. Secular government won't work, so the only chance is for us is to let "God's" government and laws rule over us? And they won't get corrupted?
But then there is unity between the different religions. Here's a Christian that has the right attitude. Where did he get that from? Does his religion need to be renewed? Or accepted and respected and left alone for him and people like him to live and believe as they do? I'm sure you'd say that his beliefs are just fine. But will other Baha'is believe that, or will they try and show him the "light"? That Baha'u'llah and the Baha'i Faith have come to replace those old, archaic, corrupted beliefs? And then vice versa, will other Christians not try and convert Baha'is to their truth, that Jesus is the only way and that you need to be saved? Can religions really get along and respect each other even though they believe different things?