The mathematical evidence against what you're saying is overwhelming. Players that say what you're saying are players that don't know how to use stack combat to its potential. But this thread is about railroads. It's yet another mechanic where civ 4 let you play the game while the design in civ 6 obstructs you from playing the game with rote inputs. Not only did railroads save time, they were integrated in a system that greatly reduced number of necessary inputs. Not just stacking, but waypoints as well. It made defender advantage more meaningful and the threat of a player's movement from fog on rails was significant. All gone. You move slightly faster and ignore terrain now, but have to keep your units on that line so have fun with the extra micromanagement of simple unit movements between fronts.