Civilians casualties are unavoidable in urban combat, especially somewhere as densely populated as Gaza. However, for civilian casualties to be this high just shows how negligent and reckless the Israeli's are being. I don't believe they are targeting civilians specifically, but at the same time, I also believe they dont care if innocents die as long as their primary target gets hit. There are munitions that can target ppl on a specific floor without taking out the whole building. They don't need to cut off power and water to the entire area to fight. Israel are bullies, and their "operations" are counter-productive, as they create more fighters, rather than eliminate them.
I also agree with the bomb shelters idea, but they will be targeted as well, with the Israeli's justification being that they were used to stash weapons, terrorist, etc. However, if some internationally recognized organization like the Red cross managed them, it's a real possibility.