Questioning Israel

I've payed some attention to livestreams of both Israel and Gaza, the ever-changing headlines of CNN,and the ongoing tensions of Israel with the rest of the Middle East. There's one question I would like to ask though...
Why blow up Gaza?

We all know Hamas use their own civilians as human-shields and how their agenda has the primary goal of destroying Israel, but why bomb it? We're just basically wasting Gaza's civies and Israel's firepower. Why not just invest fully in protecting Israel?
They've already built what I heard is called the Iron dome and other missile-intercepting weaponry which prevent of Hamas rocket/missile strikes very efficiently (according to CNN and Israeli Officials) yet they continue to bomb the city even though Hamas hides under nonmilitary buildings while also firing back at Israel.
It seems this will just carry into a never-ending chain of innocent deaths and war-debts.