VistA is an old system, and it's definitely "aging." But the thing is that it actually works really, really well. For instance, it kills a remarkably low number of people, which is one of the benchmarks I personally value in an EHR.
One of the interesting things about this is that, from my perspective, VistA's sort of a mesh of servers rather than the hierarchy we might expect from a federal system. Perhaps that's because of the complex interplay between federal and state and local laws. But anyway, there's probably a "station" for VistA near you that serves your area, and that's very similar (though not identical) to the "station" in the next neighboring area/metropolis/state/whatever.
But weirdly it seemed like the plan to roll this out was to replace all of the functionality at a given VistA station, rather than to do a strangler fig sort of thing and work on supplanting VistA's functionality in a specific functional area (whether locally or nationally). I don't know if that's because of the aforementioned complexity of laws, or the complexity of how the system(s) is/are administered, or other reasons that would elude me.
It's, uh, it's a fun situation.
VistA EHR works reasonably well for end users but the problem is that the underlying platform is kind of a dead end. There's no practical technical path to keep it moving forward with major new enhancements (some of which are legally mandated for compliance). Hardly any developers have the platform skills, no one wants to learn (career suicide in most cases), and modern tools don't support it. It's a shame but that's the reality.
https://worldvista.org/