Where are they going to go? The country is surrounded on 3 sides by the enemy with the sea on the 4th. It's one of the most densely populated areas of the world already. And they have food and water issues.
Sure...... just roll on over to the still functional supermarket and use your credit card to stock up on a few weeks worth of supplies. Hop in your SUV and stop by the functional petrol station to fill up and get some extra.
Take the coastal highway for a scenic, peaceful drive down to your winter house until it blows over. Maybe your friends are going too so you can have a BBQ.
The border is closed. And where and how exactly are you gonna house and feed a million people? And how will you move a million people, including the elderly, children, pregnant women? The infrastructure there is shaky at best on a good day. And all that is besides the fact that a lot of the excape routes have been or are actively being bombed to hell.
This is pure genocide that's happening. Israel was already systematically wiping out the Palestinian people and now their plans have just been accelerated.
The UN and other organizations have already said its impossible. The casualties of an evacuation of this scale (with Israel's siege still ongoing, mind you, so no food coming or going, in a region where in the best of days 80% of the people are dependent on foreign aid) would only be slightly less than the casualties of a ground invasion of Gaza with the residents still in it.