No, armies don't always destroy civilian areas and populations.
Yes they do in modern warfare.
It's not the 1800's. They aren't meeting on battlefields in open paddocks.
There would be more IDF lives lost but I was referring mainly to more time, more personnel, and more money. But Israel (and Gaza) would likely have a much better outcome, eventually. Guerilla warfare can continue even in very heavily damaged areas, unlike sustaining large populations, so heavy bombing and artillery campaigns on civilian areas do far more harm to the civilian residents than the terrorists (whose welfare is supported logisitically as much as possible, at the expense of the civilian populace). If Israel is serious about getting rid of Hamas they will probably need to fight door to door, eventually, at great expense, so they should have just done that and saved a lot of innocent lives.
So they fact that there would be more IDF lives lost then that's why it would be strategically a terrible ploy for the Israelis.
You'd make a terrible military leader if you would rather your own countrymen die in far larger numbers than they need to because of your incompetent strategy.