As far as I know, gravity build their game without utilizing the GPU power at all. It could be because RO is an old game, 20 years ago a gaming video card is such a luxury. But even so, my friend that played RO2 (2013~ second version) experienced the same thing. He spent $1000 and bought the top gaming video card at the time but WoE still lag like hell for him.
There is a guide in this forum somewhere that teach you how to make the game make use of your video card, I am not sure if that still apply.