While the Pittsburgh Pirates history of starting pitchers is not as deep and rich as their history of hitters is, the team has only had two Cy Young Award winners after all, they have still had many starting pitchers who were some of the best of their era. This includes pitchers such as Babe Adams, Jesse Tannehill, and Sam Leever. Even their recent postseason appearances in the mid-2010s was driven by some of the best pitching staffs in the National League.
But comparing pitchers from different eras is way harder than comparing batters from different eras.