No country has “the right to exist”, ever. Countries, provinces/states are political formations to serve the needs of ethnic populations, sometimes through conquer. But I’m the 20th and 21st century we as evolved humans decided this was a barbaric practice when done by war.
We have peacibly reformed Germany, peacibly fisdolved the USSR. Other nations have voted to (not necessarily successfully) to separate or join as well.
That said, war and terrorism are how we are watching the region of Palestinian mandate be turned into state(s). It’s been ugly, demoralizing and dehumanizing. There is nothing moral nor ethical about 6 million refugees, and an apartheid government that is made for a migrant nation on top of an ethnic cleansing project. From the beginning even during the Mandate period Jewish anti-zionists in the Holy Land said a political ethno-religious state was a bad idea. They weren’t wrong. You cannot be moral nor ethical (and neither can your military) if you terrorize inhabitants of the land to cleanse it. This goes also for the Palestinian side because there have always been three religious inhabitants since the rise of Islam on that soil.