is that due to not having a lot of memory
No, because you don't need a lot of memory with a bus that big. This graphics card is a few years old, and doesn't even compare to the gtx 1070 and 1080. I would suggest only running this card at either 1080p or 1440p max.
HOWEVER, if it were me I wouldn't purchase this card for a couple reasons:
1. You need a beefy power supply as this gpu draws an immense amount of power.
2. This gpu will generate immense amounts of heat within your case, so you better have adequate cooling.
For these two reasons I wouldn't purchase this card as the power and thermals to performance isn't justifiable.