There's a hard physical limit (speed of light) on latency that we can't do anything about. Higher bandwidth deep space communication gives us the ability to recover more science data from robotic missions, so it's worth working on.
They actually improved the data transfer latency considerably. An earlier version of the DSOC ground receiver was designed to dump data to a hard drive that would then be trucked over to Pasadena. Some joked that more bits might be lost on the I-210 freeway than between the asteroid belt and Earth.
It's good they're improving throughput/bandwidth but it doesn't help the big problem which is the latency.