Actually, the Heller decision did not reverse the 1939 Miller decision. It didn't need to because some of the lower courts have been lying about the Miller decision for seventy years.
The appellant in the Miller case was the government. The District Court had simply ruled without much trouble that the Second Amendment protected Miller's possession of a short-barreled shotgun.
The government appealed directly to the Supreme Court (bypassing the Circuit Court) and made two claims in their plea to overturn the District Court.
First they claimed that Miller could be tried because he was not a member of the Militia, so his possession of a short-barreled weapon was not protected by the Second Amendment.
Second, they claimed that Miller could be tried because the short-barreled shotgun was not useful to a Militia and therefor the possession of such a weapon was not protected by the Second Amendment.
Significantly, the Miller Decision did not address membership in a Militia. They only questioned whether the weapon was useful to a Militia, a fact which would be irrelevant if Miller himself wasn't protected by the Second Amendment. The case was remanded back to the District Court to make a factual determination, not about Miller, but about the shotgun.
For the next seventy years lower courts have simply lied about what the Miller case decided and the liberal media supported the lie. I'm not aware of ANY Supreme Court decision which has treated the Second Amendment as anything other than an individual right.
What the Supreme Court DID do was fail to correct the lying lower courts for almost a century.