Representative democracy is for me a nice concept on paper and failed idea in reality. It might have worked in the fledling phase of young democracies, when parties were still young and decisions were really being made bottom-up.
But nowadays parties are in most countries really top-down. You cannot rise up in the ranks if your opinion is too far away from the leading circle of a party; you simply won't get the necessary support to run for whichever mandate you want to. Then there's also the disastrouse instrument of the party whip.
This top-down hiearchy destroys internal discussion, makes it hard for people of different opinion to rise and creates a monoculture of opinions and stuff. It means that in reality a few people nowadays are shaping what a party is about, how they are going to vote and such.
Representative can mean two things IMHO by the way:
a) representing the constituency and
b) representing the society.
While a) might still be possible if a MP is working hard enough, b) definitely is not.
Most parliaments are not representing a modern society; in reality those are mostly stuffed with elder, white men who are typically teachers, lawyers or have been officers. Most parliaments are lacking really young members, women, minorities of all sorts and members of the poor working class. They are in that regard not representative at all.
What we really need today are other forms of democracy which are quite more resilient against the inteference of certain circles and really are working for the good of all people of a society. This is possible; representative democracy is definitely not the way to do it.