Why is Ukraine powerless against Russian Onyx missiles

the missiles being currently used to attack southern Ukraine are being fired from the K-300P Bastion-P mobile coastal defense vehicle, it is hardly possible to shoot down Onyx missile at high speed and at low altitude with the available air defense systems in Ukraine.

The Bastion-P (NATO reporting name SS-C-5 Stooge) is a ground-based coastal defense system that can fire Oniks anti-ship cruise missiles, which also have secondary land-attack capabilities.