Cavalry was replaced by mechanised cavalry, the concept still exists with better equipment.
Drones don't replace artillery, they are a new weapon, just like air dropped bombs didn't completely replace artillery. An army with drones and artillery is more capable than an army with only drones.
The main difference is that armies learnt how to counter artillery: keep squads separated enough, assault units more dispersed, dig more foxholes, etc. They haven't learnt how to counter drones yet, the arms race for that is raging on Ukraine.
Drones don't replace artillery, they are a new weapon, just like air dropped bombs didn't completely replace artillery. An army with drones and artillery is more capable than an army with only drones.
The main difference is that armies learnt how to counter artillery: keep squads separated enough, assault units more dispersed, dig more foxholes, etc. They haven't learnt how to counter drones yet, the arms race for that is raging on Ukraine.