Instead of dropping tons of expensive guided bombs and shells, attackers will drop tens of thousands of cheaper small anti-personnel hunter-seeker drones that can not only seek out human targets but wait in low power mode for a target to appear if it can't identify one at first. It'll make most kinds of static installations and defenses untenable. Units will have to constantly be on the move and camouflaged, and avoid giving up all kinds of life signs like sound/gunshots, thermal, RF comms, etc. The smaller drones will be able to help larger drones with targeting any armor they can't handle themselves while acting like free flying land mines.
I agree that it's a software problem. The Slaughterbots video [1] is already six years old and all of the pieces to make killer drone swarms were already there (just not as miniaturized as the video). Now there's data in Ukraine about how well individual drones work; AI is getting better and better; the compute is getting cheap enough to just slap on a drone; SOTA single use aluminum air batteries can already enable drones with much longer flight times than consumer batteries. All the pieces are there to make a nightmarish weapon that changes warfare as much as the machine gun, land mine, or air support.