You have obviously never served in the military, certainly in a combat role (as I have). This is why it seems strange to you.
Depth is a fundamental requirement for any defence. This is a basic principle of warfare.
The IDF tried to do the impossible (using technology & firepower as a substitute for depth) and on Oct 7 it blew up in their faces.
Depth is essential because ANY position (observation or firepower) or armed force that is located on a fixed line (border) can be attacked and destroyed by an attacking force in a surprise attack.
ONLY by having obstacles to movement behind that fixed line and hidden firing points in depth behind that fixed line can defending forces have the time and space to organise defensive forces at the points of concentrated attacking forces.
To attack you must concentrate your forces but the attacker has the advantage of choosing where to concentrate and break through. Depth gives defenders the time and space to organise.
Without it you get what happened on Oct 7 when the enemy breaks through to rear areas and causes havoc.
The IDF is the best army in the world, but is still subject to the basic, timeless realities of warfare.
RE: Israel created Hamas as justification to genocide the Palestinians