Israel is too small to be defensible. It has no strategic depth, being sandwiched between the Jordan and the Med.
Israel is only about 270 miles long with a maximum width of about 75 miles.
Modern rocket artillery, like the HIMARS, can reach any point in Israel from outside its borders.
When you look at the Iranian missile inventory you see they can easily overwhelm the Iron Dome and have enough left to bounce the rubble a few times.