The hostages are such a complicating factor. Last report I saw on CNN's webpage suggested that Hamas has at least 166 hostages. Some are military service members (both men and women), but they also have kids, old people, even some entire families.
And some are foreign citizens, although I don't know if that means they are exclusively foreign or dual citizen. At least one German national, for example.
And they'll distribute them all around Gaza in singles and pairs. Not keep them all lumped together where Israel can rescue them all in a single raid. And move them around often such that by the time Israel learns of some of the locations, the hostages will already have been moved to new locations.
Israel is very, very angry. This is being compared to a 9-11 level event for them. And Israel has a very effective military. Israel doesn't target Palestinian civilians and goes to some lengths to prevent that, but does accept that a fair bit of collateral damage among Palestinian civilians happens anyway due to dense living conditions and a wide grey line between combatant and non-combatant Palestinian people.
But Israel also has a history of going to great lengths to prevent harm to its own people. In 2006 Hamas captured one single Israeli soldier (Gilad Shalit). Israel raided Hamas to get him back but didn't succeed. They then spend five years negotiating with Hamas and eventually
exchanged Shalit for 1000 Palestinians in Israeli custody.
So Israel is not going to go in so kinetic that they start accidentally killing hostages. And with those hostages distributed throughout the strip and being moved around, that will be a pretty severe limitation on the use of Israeli military force.
ETA To add to this: Israeli settlers in the West Bank are probably just itching to use this as an excuse to start something there. Not that the settlers ever need much motivation to be ******** in every way possible to the Palestinians around them. That could be enough motivation to draw in Hezbollah, a much more dangerous enemy than Hamas could ever be.