Others have suggested greasing the dowel or using bearings, and if the issue was friction, then they'd be right.
If the issue is inertia, then this won't help. Accelerating a given mass to a given velocity requires a certain amount of energy, no matter what.
What could help is something similar to a Huygen drive, where the filament is looped around a large wheel (large enough that the filament can curve around it without breaking) which is able to move against a spring or counterweight. This would allow the movement of the spool to be "averaged out" rather than accelerating and decelerating sharply on every extrusion and retraction.