I meannnn... it doesn't force you. By default, the preventLastDirection flag is only enabled for Peach and for flight powerups, and the xForce and yForce values for the speed the player gets while jumping off a wall are also customizable, so you can easily adjust xForce to make jumps go less far horizontally.
Disabling the flag for peach simply requires copying the contents of registerAllPlayersDefault into your luna.lua and removing the preventLastDirection setting from the peach line:
aw.registerCharacter(CHARACTER_PEACH, aw.createFrameTable(-6, -6, -6, -6, -6, -6, -6), {allowSpinjump = false})