2 handers will always be popular because...
They're big ass swords. People always like big ass swords in any game
One of the key game mechanics is manual blocking and some people play simply because they like how the melee combat works
The animations feel "right", like they fluidly chain together and they look good.
All the attack directions are decent
With polearms you get the weapon caught on stuff
You get extra weight because of the lengths of poles which doesn't translate into better weapon performance (its just to nerf long spear/pike but affects all poles)
The attacks don't feel as fluid as 2 hand/harder to feint convincingly with
Lots of cheaper poles that don't perform anywhere near as well as cheaper 2 handers
Hardly any Unbalanced weapons is a big + for me
Versatile weapon selections. Anti cav, dueling, support, shield breaker
I don't think you should nerf based on popularity alone. The manual blocking mechanic and the way the weapons look and feel is probably the main thing that makes them popular