It’s not designed for ground/building attacks. It’s a very low yield explosive designed for missile defense. They should just sell keep selling them off to 3rd world countries, I was under the impression that they had already done that, as they are obsolete for advanced current defense usage.
No, the S300s are not ideal for the ground attack role, but they are available. Russia seems to have lots of them in stock.
Maybe they should have sold them off in a fire sale years ago, but they didn’t. You would have to take that up with the Russian government.