WHAT DO MPs REALLY DO?

It's said MPs don't really do anything but talk all day long and it's seems they can never agree on anything. If by any chance they do agree it becomes law.
Do we really need them?
When we had a king ruling we didn't need them then. All he needed was his advisors which to be honest are what MPs are today.
Was it one man's vision for the future of this country or is it still an insane idea that's been put into practice?
Are MPs really as deaf as we think they are?
We are always complaining that MPs don't hear a thing we say, and that they always seem to assume what the people want or need.
So what do MPs really do? Me personally I'd love to know.