Not easily, long range 'theatre' drones are built on lifting body designs, planes essentially. Those can't manuver that much so they can't sneak in. Hardened shelters stop Shaed style drones and missiles easily at comparatively low costs.
Modern tactical drones are often quad copter style and with fibre-optic wires are good for around 30km. Those can wriggle through pipes like a distopian buzzing xenomorph horror film. And yes, against an enemy with plentiful tactical drones infantry operations are a slaughterhouse. Ukraine managed a spectacular operation sneaking a truck load close to a Russian air base but even that would have been fooled by cunning use of doors and a roof.
Traditional military kit isn't all obsolete yet, but drones are the modern version of the machine gun. It makes defence much easier, assuming you have ammo.