But it's still only designed for vertical resolutions.
Do you have a reference?
Systems such as the Avidyne 600 give you a reasonable azimuth reading, from what I have seen. Way better than nothing which is all we get most of the time it is most needed. Way better than an RIS under which the controller is not obliged to give you every contact because it is subject to controller workload.
The majority of traffic is not spotted visually even when you have a bearing (from TCAS or from RIS) even if you have four people in the cockpit all "knowing" where to look. A 30 degree turn or a climb/descent is easy enough to implement.
Don't knock a piece of technology just because it isn't perfect. One day it might be much better - when everybody is emitting GPS lat/long over Mode S 1090ES, just like airliners do already. But the altitude value will still be baro derived (instead of a precise GPS value) so it will be +/- 200ft, so if flying at 2400ft under the LTMA the smart choice will be to turn rather than a level change.