To continue your analogy, Israel tried to "graduate" Gaza to adulthood in 2005. The army removed all Jewish settlers and settlements, and all military presence, and left the Gazans to form their own government. Gaza held elections that were judged to be free and fair by international observers.
Unfortunately, Gazans elected a Hamas, a recognized terrorist organization dedicated to the destruction of Israel. Don't get me wrong, I can understand if Palestinians feel sore about the creation of Israel on some of the land that they desired for an undivided Palestinian state. But 10 million people live there now, including generations of Jews who have no other home, many of whom were expelled from other Arab countries when Israel was founded. A settlement between Israel and Palestinians will require compromise, but Hamas is not interested in compromise. Hamas dedicates every available resource towards an absolutist goal of destroying Israel.
Moreover, Hamas does not see itself as having any responsibility towards the people of Gaza. It builds tunnels to protect its fighters, but considers it the UN's responsibility (through UNRWA) to protect its civilians. In this sense it operates differently from almost any government in the world, in that it is not actually trying to build a society and govern it. In the eyes of Hamas Palestinians are in a war that has been going since 1948, and this war will continue until Israel is destroyed. It considers all of its people refugees and wards of the UN until Israel is destroyed.
I have plenty of criticism for Israel, primarily that it builds settlements in the West Bank, sabotaging prospects for a future Palestinian state. But it's hard for me to fault Israel for acting as the legal guardians of the Palestinians when I witness the Palestinian's disinterest in actually building a state that could coexist with Israel, not to mention the means by which they enact their resistance.