What is democracy in the eyes of a common man? To him, it is the system of government which allows him to make laws for himself and his fellow men, in short a system which allows him to interact with the constitution. Though this definition may not be followed in all the countries who claim to be democratic but more or less, most of the people there also want this definition to be applied there.
Let us see now whether such a system would be fruitful or not. Suppose there was a scientific hypothesis which was presented and the proofs of it were given. Some proofs included were such that if the common man looks at it, he is amazed at how perfectly it fits in with the scientist's explanation. On the other hand, when another scientist, who is highly qualified in this field, investigates into them, he does not find it difficult to declare those proofs bogus.
Now, if we were to go with the concept of democracy, we would have to show it to the public and ask them to vote on whether this should be declared as a scientific law but that's not how it is done. Why? Because the common man has no idea about the complexities of the situation. However, when it comes to politics, there is a double standard. Does every adult get a PhD in political sciences on getting his national ID card? Or maybe just as the genitals develop when a person reaches puberty, a political instinct also develops in the person on reaching the age of 18? That would be a better explanation as it would account for the different age for voting in different countries.
OF COURSE, ALL THIS IS RUBBISH!
No matter how much I try, you won't be convinced by it. Yes, it's true that your experience makes you mature but you don't become an expert.
What do the people say in response then? We aren't making the laws, we're just electing the experts who will make laws for us but do we also elect the scientists and other PhDs on whether they are capable enough or not? Of course not!
Note that I'm not touching the topic of how a class of people oppressed other classes when they were in power and vice versa. You can go back to the history books for that.
Having said that, there must be a solution. We can't just live without a law, that's for sure. Well, let's carry on with our example of the scientists.
Suppose the scientists comes up with an appliance and he sells it to a few people. Will he ask the customer to write the user documentation so that the other users may benefit from it. Of course not! He will write it himself mentioning how it should be used, what to do when a problem occurs and so on and so forth.
Similarly, Allaah Azzawajal created us (for those who disagree with this fact, go to the contact page and email me. I might be of some help and if I'm not, we'll find someone else, inshallah) and he gave us a few appliances, our soul, our body, the land we live on and the list goes on.
Now that we've got those stuff, we won't start making a user documentation, or in general terms a constitution, for us. We should logically follow the constitution provided to us by our Creator which is the Qur'an. Furthermore, we're not supposed to extract rulings from it ourselves as was mentioned before and as is also mentioned in the Quran:
Ask those who know (i.e. the experts) if you do not know (16:43)
That is where the Prophet Muhammad (may peace and blessings be on him), the Sahaabah and the righteous 'ulamaa come in.
The conclusion to all this is that the only acceptable law, at least to the Muslims, should be the law of Allaah. With regards to the claim that Islam is oppressive, anyone who investigates into this matter will know that it's a mere fallacy.