This means that enb does not have access to the depth buffer so the dof effect thinks everything is homogeneously in the distance or very close to the camera (the depth buffer is full white or full black).
If you are forcing AA through your driver no general postprocess injection will have access to the depth buffer.
But with enb you will get blurred UI even if you manage to get it to work (this requires (after disabling forced AA) a specific version of the gta sa enb d3d9.dll and non-tinkered-with slrr exe (I dont really know which though))
You should consider using the slrr adapted reshade LINK
and if you prefer the mainstream slrr aesthetic: LINK
