What you seem to fail to understand is that Hamas is dedicated to the goal of eliminating Israel — wiping the country off the planet — making this an existential crisis for Israel, not something to fit into your narrow and weird definition of “just war.”
What you want sounds more like a soccer match played among second graders, where fairness is emphasized over winning.
I understand that, and indeed every time rules of war are brought up someone would say that it is not a soccer match. Hamas, from its own perspective, would also point out its own reasons to violate the rules of war as it resorts to terrorist tactics and sets goals that are genocidal.
This is precisely why rules of war matter. They especially matter for the survival of Israel, who has not done well in the eye of public opinion lately.