Whether they’re more-efficient is going to be depend on the specific case in which they’re being used.

The actual quote in the article reflects that, is more qualified than the title:

“They work sometimes even more efficiently than artillery,” he told Newsweek. “So, FPV drones are indeed a tech revolution, even though the tech itself is quite easy. But it turned out to be very efficient.”

• An artillery shell moves a lot faster than a drone does. If one needs to make something explode soon, then that time may make artillery preferable.

• An artillery shell is going to be harder to shoot down than a drone is (and my guess is that this factor is only going to become more-prominent; it looks like counter-drone systems are getting attention, and the article mentions them).

• An artillery shell is going to be generally less-affected by jamming than a drone is (though there are some guided artillery shells that make use of GPS or the like in Ukraine, like Excalibur).

• As far as I know, there aren’t artillery shells that make use of two-way radio communication, whereas FPV drones do (or at least can). I’m not familiar with what the state-of-the-art is for identifying operator location from their radio broadcasts – and separating the operator from the transmitter could maybe help mitigate this – but I’d guess that there are probably efforts to identify an operator’s location.

On the other hand:

• A drone can adjust its target in-flight to deal with movement of the target. Most existing artillery shells cannot do that (though some do to a limited extent; BONUS, one of the shells used by Ukraine, identifies and targets vehicles during the last part of its flight).

• A drone doesn’t require the degree of (visible) infrastructure that artillery does.

• Units launching drones can be more-dispersed than units firing artillery (each unit could just carry a single drone, which isn’t likely practical for a tube artillery unit).

• A drone can be launched more-quietly.

• A drone can fly at low altitude. Russia has counter-battery radar, as does Ukraine; a shell fired by artillery can be seen on such radars, and travels in a predictable, ballistic arc, exposing the location from which the shell was launched. While there are also ways to detect a drone, my guess is that in general, artillery firing at a target runs more risk of exposing its location than someone launching a drone.

• A drone might have better range than artillery. Artillery shells need to have their kinetic energy imparted at the time they are fired (well, mostly, since there are things like base bleed shells or rocket-assisted shells). Air resistance grows as the square of velocity. Drones don’t have to fight that particular laws of physics, since they’re keeping a lot of their energy in the form of chemical energy for much of the flight. There are longer- and shorter- range drones in use in the conflict, and theoretically one can scale up artillery as well, but broadly-speaking, I’d say that drones have more potential for longer range than artillery.