The Ukrainians have been conservative with all their SAM systems. Drones have been dealt with by much simpler point defense systems (from manpads to German Gepards to old style light AA guns).
The SAMs have been mostly used vs cruise missiles.
Part of the problem is that though Ukraine has other SAM systems, including Western ones like NASAMS and IRIS-T, only the S300’s and Patriot have the range and coverage to deal with cruise missiles over broad areas. They are extremely low, by now, on S300 ammo.
The Ukrainians have been conservative with all their SAM systems.
The Ukrainians have not been conservative with anything. They have blown through all the equipment that the western allies could give them. They are low on just about everything to do with air defense, and what's left is in good part reserved for Kiev. They are low on just about everything to enable their ground forces to wage war effectively. It is sort of what happened to the Confederate army at the end of the Civil War. In addition to a shooting war, there is a war of logistics.
Where are they going to put their air defence? They relocated many of the few Patriots they had towards trying to stem the rout at Avdiivka. I think two or three got destroyed in transit. A couple more were Iskandered, I believe.
Currently, senior Uke leadership is on the run. Nowhere in the country is safe from a hypersonic. The troops and front line fortifications are FABed with impunity. The entire electric power generation system is rapidly being degraded to functionally dead. I assume the bridges are next. Where is their air defence?