Ukraine has also not yet attempted to hit Moscow (the city, not the ship) with missiles.
Once a nuclear bomb is used, a lot of gloves will come off, not just the Russian ones, and so far Ukraine appears to have a lot of extremely competent military partners and Russia has a reluctant Belarus.
What missiles capable of striking Moscow does Ukraine have? It's 500km from the closest point within Ukraine's borders. That's at the limit of long-range variants of Iskander, and Ukraine only has older stuff like Tochka.
Once a nuclear bomb is used, a lot of gloves will come off, not just the Russian ones, and so far Ukraine appears to have a lot of extremely competent military partners and Russia has a reluctant Belarus.