well I don't think they do nothing, but I do want to get rid of them, and I want all their stolen land to be returned to the public, to whom it rightfully belongs.
The crown estate isn't owned by the monarch in the sense that ordinary land is (it is not her private property). The Queen cannot sell any of the assets and she does not receive the revenue generated. Instead all revenue goes to the government, and the royal family receive a payment in exchange (ie the civil list). Although that's soon to change and they will receive a proportion of the revenue instead.
So what exactly is the civil list money used for? I'll quote the royal website on this:
"About 70 per cent of the Civil List expenditure goes on staff salaries. It also goes towards meeting the costs of official functions such as garden parties, receptions and official entertainment during State Visits. The Queen entertains almost 50,000 people each year."
Only the Queen & Duke of Edinburgh receive this money, and it is used solely to fund her responsibilities as the head of state.
You see I'm still not quite understanding your rationale here, as I said earlier, do you think the Queen does a bad job as head of state?
If you want to know more about the royal finances, or the schedule of the royals the information is all freely available.