How is it “indiscriminate” if solely Hezbollah operatives were targeted?

Because said operatives were often within exploding distance of civilians when the pagers were detonated. Shrapnel, even from a small explosion, can be deadly and has a fairly large range. Especially if you don’t have line-of-sight to your target before detonating the device; you have no idea what or who is nearby when it goes off.

“Explosive” and “targeted” generally don’t go hand-in-hand.