A reusable Zenit or Energia would have been a real game-changer back in the 80s. Russian launches would have cost a fraction of what they were in the west. With cheap launch costs, MIR would likely have been maintained and expanded; maybe even to this day. The ISS would likely not exist since one of its primary goals was to engage the Russian space industry and prevent it decaying away to nothing. With Russian primacy in space, perhaps we'd see more of the 'exotic' Russian space ideas realized... like Kliper, TKS & Polyus.
There is a great episode on Energia/Buran vehicle that goes in depth and interviews the key players. It's in Russian, but the "auto-translated" subtitles are quite good.
But the required metallurgy is no longer exclusive to Russian engineers -- SpaceX's Raptor (which is a full-flow staged combustion engine) has an oxidizer-rich preburner on the oxidizer side of the engine.