If you want to have a discussion about historical weapons usage, then spears saw the most effective use during the Roman Empire, as the second flank behind a shieldwall – a tactic that would be pretty effective against zombies to be sure.
Despite the popularity of polearms in D&D manuals, there’s very little difference in the way they are wielded in combat, and as druidniam points out, during the middle ages, they are primarily used from a position which grants distance between them and the target, and wasn’t very useful if they came in close.
Regardless, this is a conversation about game balance. If you’re going to have a Reach weapon, you should have multiple reach weapons to provide an illusion of choice. And honestly, while slow, weighted chains aren’t that difficult to aim at targets 6-10ft away. I do this regularly as part of my performance art.