Israel isn't going "scorched earth" and there isn't a number of dead civilians which is "enough". This whole meta-commentary is false., this is not some sick payback on the Palestinian people.
How it started
In 2005 Israel left Gaza because it had enough. 20+ years of peace offers, most of them contained at least 97% of the 67' land, and yet time after time the PLO said not. Israel had enough of corrupt Palestinian leadership, so they thought that if they just left them alone, the Palestinians would leave Israel alone. It might not be real peace, but the Palestinians will have their state, Israel will have theirs and the whole thing will be behind us.
So Israel dismantled all of their towns, ethnically cleansed Gaza from Jews, and removed all army presence in the area - full withdrawal. Israel left beautiful empty towns where Palestinians could live, with fields and greenhouses where they could farm. In 2005, the people of Gaza were set free. No blockade, no Israelis, no Jews, no oppression, and a clear-cut border. This plan had a second phase - leaving the West Bank and by doing so, completely disengaging from the Palestinians. Gaza was the test case. And yes, Gaza was free... for about 5 minutes. Their freedom started in September 2005 and ended in January 2006 when they elected Hamas in their first and only election. Hamas attacked Israel over and over again with rockets, as a result, Israel placed a blockade on Gaza, and that's how most of Israel became right-wing leaning. When you give everything and get rockets in return, people's minds change. Israel just gave up on the Palestinians.
Since 2007 Israel tried to manage the Gaza threat from afar. A blockade was placed to prevent weapons from getting in (even though they still go in through the Egyptian border), a wall was built, and the Iron Dome was developed to protect its citizens from rockets. Every once in a while Hamas would kill a few Israelis or fire so many rockets the country became paralyzed, and Israel would start an "operation" that would last a few days or weeks. Hamas would fire rockets, Israel would blow up launchers, and ammunition, Hamas government builds, etc all placed within the civilian population of course. A few Israelis would die, and hundreds of Palestinians would die, and after a few days, a cease-fire would be signed. Palestinians would rebuild, Hamas would re-arme itself, and 2 years later it would happen again. This was the Israeli existence for 15 years, living in a loop with Hamas on the border.
How it's going
After October 7th everything changed. At least 1,500 Hamas terrorists bomb rushed the border - intelligence failed, the army fell, and 1,500 terrorists had the time of their lives for hours on end, having their ways with innocent civilians. The people who live near the border can't go back to their homes knowing that at any point terrorists can rape, kidnap or kill them. Israel's perception of Hamas has changed, it's ISIS now, and how the hell do you live next to that?
So no, there isn't a number of civilians which is "enough", because civilians are not the target. This is not a random "scorched earth" campaign, this war has a goal - destroy Hamas and release the hostages. Without achieving these goals Israel will never stop.
Hamas has over 20K terrorists in their military branch (Izz ad-Din al-Qassam Brigades), and thousands more in their government branches. They have whole neighborhoods built just for Hamas members and their families (which you saw flattened), and there are hundreds of government buildings, rocket launchers, ammunition depots, tunnels, bunkers, and so forth; all of them are placed inside cities, neighborhoods, under hospitals, and mosques. If Israel destroys all of them, you will see over 30K dead, more flattened neighborhoods, and unfortunately, collateral damage of hundreds if not thousands of civilians. Doing all of that might seem random without the context, but it is required in order to get rid of Hamas.
Hamas will lie, give false fatality reports (we all saw what happened with the hospital), and will magically transform Hamas members killed into civilians. Their rockets will fail (currently 20% failure rate according to the IDF) killing their own people, ammunition depots under buildings will explode, and the usual Hamas PR campaign will wage for months. All of that while their leaders are smoking cigars in Qatar. This war will wage for months, if not over a year, but hopefully Hamas will be (virtually) gone when it ends.
And you know what? As much as Israel has been suffering at the hands of Hamas, Palestinian citizens have been suffering too. Years of living in fear, crushed by the boot of Hamas, used as human shields, and their supplies stolen in order to build tunnels and rockets. In the coming war a lot of Palestinians will die, but unlike all the other "operations", when it ends the people of Gaza will actually have hope. Israel is ripping the bandaid and it hurts, but after it comes off Gaza will have a (second) chance to heal.