When the Prophet was in Makkah for the first 13 years, people used to drink but no command related to prohibition of drinking was revealed. People used to also take interest. The society was not prepared to leave drinking and taking of interest. One has to see the level of preparation of a society. The nature of preparedness of a society will determine the kind of law or system to be established there. If you set a standard and seek to impose it on a society, that would be wrong. The Prophet never did so.
Prophet's wife Ayisha said: The first verses to be revealed in the Quran dealt with belief, moral values and common brotherhood. When the society was perpared and people began to accept Islam, then verses dealing with lawful and unlawful were revealed. Had the verses spoken about not committing adultery and not drinking wine, وَلَوْ نَزَلَ أَوَّلَ شَيْءٍ: لاَ تَشْرَبُوا الخَمْرَ، لَقَالُوا: لاَ نَدَعُ الخَمْرَ أَبَدًا، وَلَوْ نَزَلَ: لاَ تَزْنُوا، لَقَالُوا: لاَ نَدَعُ الزِّنَا أَبَدًا، (Sahih al-Bukhari 4993) People would have said: We will surely not abandon adultery, we will surely not leave wine.
What does this mean? The social system of Islam is relative and not real. It depends upon the social condition. This is why, the Prophet said: كَمَا تَكُونُوا كَذَلِكَ يُؤَمَّرُ عَلَيْكُمْ (Shu'abul Iman, al-Bayhaqi 7006) As you are, so shall be your rulers.
There is democracy in Islam. In society there should be government of the people, by the people and for the people. Legal system and political system will be in accordance with people's desires. If the society doesn’t have the will for a particular system, then whatever system it wants will come in place. India has a secular system. The society here wants a secular system. This will also be the will of Islam, because this is what the society wants. As you are, so shall be your rulers. The political rule will depend upon the society. Indian society wants secularism. Here, Islam will accept secularism. If in a society people want Islamic law, then Islamic law will be observed there. This is dependent on the society. They will decide which law or legal system they want.
If sitting in a room you develop a theory which says Islam is a political system and that this system should be forcefully imposed, this is a wrong idea. When the Prophet was in Makkah for the first 13 years, people used to drink but no command related to prohibition of drinking was revealed. People used to also take interest. The society was not prepared to leave drinking and taking of interest. One has to see the level of preparation of a society. The nature of preparedness of a society will determine the kind of law or system to be established there. If you set a standard and seek to impose it on a society, that would be wrong. The Prophet never did so.