Why is the Aran class so unpopular?

I just made a Kaiser and... I have never been more in love with a class in my life. It's like Aran with hitting multiple enemies and uses combos but damn is it fast. I also like that Nexon has given more "attractive" options when making a newbie char.

I think you just basically answered your own question. Kaiser has most of the same appeal of an Aran with more bells and whistles, better numbers, and some flexibility in attacking methods. About the only thing Aran has going for it over Kaiser is a more dependable stance and a level 200 mount.