Ok, I keep missing it, where is the compromise here?
If you haven't, please read the decision. Scalia does some quite involved tightrope dancing to come up with an individual rights interpretation that leads to them ordering DC to let him register his handgun while at the same time not overturning NFA '34, GCA '68, Brady/NICS, FOPA '86 or anything else except DC's complete ban on handguns.
That's compromise.