Gaza is under siege. If there were bomb shelters (don't even get me started on how they'd build enough bomb shelters to successfully protect 2 million civilians in one of the most densely populated regions in the world), does anyone genuinely believe Israel would back off? They'd say these bomb shelters are military bases being used as human shields and infiltrate them anyway.
Israel are bombing and flooding the tunnels despite telling the world the hostages are being held in them. That's how much Israeli "rulers" care about the lives of their own civilians, so let's stop pretending they care about the lives of Palestinian civilians in the slightest.
Why are we still pretending Hamas built these tunnels? Tunnels have existed under Gaza for centuries.