Why is Russia sending anti-aircraft guns ZSU-23-4 Shilka SPAAG to modern warfare?

Why is Russia sending anti-aircraft guns ZSU-23-4 Shilka SPAAG to modern warfare? Many sources claim that Russia has invested in new technologies to support production, both in the aircraft industry and in the production of heavily armored vehicles. Why is Russia sending anti-aircraft guns ZSU-23-4 Shilka SPAAG to modern warfare? Many sources claim that Russia has invested in new technologies to support production, both in the aircraft industry and in the production of heavily armored vehicles.