Grid forming inverters for providing virtual inertia are only going to get better and better, there's no reason that as those control systems improve why synthetic inertia won't be able to be basically identical to real spinning mass. In the meantime while that technology matures, synchronous condensers can provide grid inertia without needing nuclear or coal, we already have about four in Australia supporting our grid and will probably have another dozen or so built over the next decade or two.