Being prepared for this scale of operation means either having specialty firefighting planes and drones in reserve, or having other vehicles - general purpose drones or cropdusters or, heck, a Globemaster with a big ballon full of water in its belly - that can be repurposed and sent to this emergency from all over. Airships would be nice for the volume, but they aren't exactly friendly to the turbulent conditions near a fire.
The CL-415 that you shared in the link has a reported capacity around 6100 kg of water. When I searched for “heavy lift drones” I got the Draganfly Heavy Lift, which can reportedly carry 30 kg but only for 18 minutes of flight time (according to the company’s web site). I think the plane’s flight time is around 3 hours but obviously the math is a little more complicated than that.
* there aren't enough pilots
* pilots understandably don't want to fly too close to the fire
But a drone might be able to get away with carrying less water and do more of a targeted squirt.
I don’t see any reason to believe there’s a pilot shortage, and I don’t understand what’s wrong with the current targeting, or how that could be improved. There’s a whole strategy to fighting fires of this scale. I don’t think the strategies are obvious to people on the ground.