The problem with Hamas is that they don't shy away from hiding combattants in civilian clothings or use women and children as suicide bombers. There is more than enough evidence of this tactic, dating back many many years [1].
By not just not preventing, but actively ordering such war crimes, Hamas leadership has stripped its civilian population of the protections of international law.
> Otherwise, the allowed list of targets of civilians gets so wide than in any regular war, pretty much any civilian could get targeted, such as the bank employee whose company has provided loans to the armed forces.
In regular wars, it's uniformed soldiers against uniformed soldiers, away from civilian infrastructure (hospitals, schools, residential areas). The rules of war make deviating from that a war crime on its own, simply because it places the other party in the conflict of either having no chance to wage the war or to commit war crimes on their own.
[1] https://en.wikipedia.org/wiki/Use_of_child_suicide_bombers_b...