Question

why it is said that modern democracies are representative ?

Answer 1

In modern democracies, all the people do not rule because their populations are so large that it is physically impossible for all the people to sit together and take a decision based on consultation and discussion
The people may also not have the time,desire or the skills to rake decisions

Hence, in modern democracies, the population votes for their representatives in the elections.
These representatives exercise supreme political authority on the behalf of the people in India. These are the MPs