Less than 10% is not good when you consider how much does it cost in practice. Drone teams are often 2 pilots + technician + explosives technician (an incredibly risky job btw, those bastardised RPG warheads are live and sensitive) + infantry cover. At least double that if you want to strike beyond line of sight and need a retransmitter drone. Those teams can only move at night and on foot because they are actively hunted by the other side. They can only have one or two drones simultaneously in the air at best, and the drones need to get to their targets first without giving away the launch point. All of that for less than 10% success rate is not "incredibly effective".

Now compare to fire-and-forget Javelins that are way more lethal and are just something added to a normal infantry platoon.