You can do that now in the western word. Does that maker us islamic? No, of course not. It's not a uniquely islamic concept, it's a concept islam shares. And out of curiosity, since this harmony never lasted, what do you consider the last muslim state?
This is a common misunderstanding that Muslims represent Islam/God. The term "Muslim" is now just a label which means a person who follows the Quran and believes Mohammed is a messenger of God. The proper meaning is someone who has chosen to accept God and obey his revelations. This can apply to Jews, Christians, and people of other religions who have one God and have been given divine revelation. When you are not obeying the revelation of God you are just a plain believer. You can be good believer or bad believer. When you're a muslim you are both good and obeying the law of God.
There were many nations that believed in God but they were punished by God or destroyed. Believing in God does not save you. Your actions and heart save you. If you read the Quran properly God is mostly warning and threatening the believers. He's not saying oh you believe you are now saved and you can rest now. It clearly says the believers need to save themselves from hellfire.
But peoples arrogance and brainwashing from a young age makes them think they are automatically saved. A bit like Christians thinking they are saved.
It's so frustrating how much misunderstanding there is about God. Which is why God makes it a very big sin to lie in the name of God because it can take many people away from God, from the truth.