it hasn't even been 1 year since RX590 came out,
but Anti-lag for Dx9 is exclusive to rx5700 series,
while nvidia made available for all their gpus.
Nvidia released Ultra-Low Latency
Our new Low Latency Mode is being released in beta with support for all GPUs in DX9 and DX11 games (in DX12 and Vulkan titles, the game decides when to queue the frame).
Most of the Free To Play online First Person Shooters are in Dx9,
I am hoping that AMD can enable or cook a driver to make anti-lag work for dx9 titles in Polaris.
Technically the RX 590 is a three year old card, simply being and overclocked, overvolted, and rebadged RX 480 from 2016. As for why it doesn't work in DirectX 9 titles the way nVidia's does, nVidia has had an "anti-lag" setting for years (“Max_Prerendered_Frames = 1”) while AMD has not, and as there still is not a WHQL driver for the RX 5700 series, and given how little resources AMD has devoted to consumer graphics, there is no telling when or if previous cards will get this feature officially.