Although our political system (sort of) works on the premise that we elect representatives as individuals, the reality is that most of people vote for their party of choice at any given time. That's why people feel very annoyed and betrayed if their chosen representative defects from one party to another after being elected.

Often, people will know little or nothing about each party's chosen representative for their constituency, and even if they do know them and don't particularly rate them, they will still most likely vote for the party they want to control the country. Therefore, the power to improve (or indeed diminish) the quality of parliamentarians lies with the political parties themselves through the quality of the people they select as candidates.

As cher1 says above, all of the political parties make bad selections, arguably more now than ever. I believe the quality of parliamentarians has declined because fewer people are entering politics for the right reasons to serve others, and more are simply chasing money and power to serve themselves. That's probably why even the biggest parties in parliament seem to have more and more difficulty finding even one impressive leader these days, despite having a pool of hundreds to choose from.