But the basic finding that the inequitible application of the death penalty constitutes "unusual punishment" is sound.
At most, the Justices could have found that the death penalty was inequitably applied in the case immediately before them. They had no authority to impose a national moratorium on the death penalty, merely because the defendants before them at the time may have been treated unfairly.
There was ample evidence of inherent problems in sentencing regimes that were being used, especially in the Southern States. If a death penalty statute or its general application is violating equal protection, the statute cannot be allowed to stand, and thus must be struck down.
This has the obvious effect of creating a "moratorium" on the death penalty. It perhaps should not have created a national moratorium in the way that it did, but rather said that Georgia's regime was and laid out a basic framework for the Circuits to follow to decide whether such equal protection problems existed in the other States, but the underlying judgement that some sentencing schemes, and specifically the one of Georgia, were violating equal protection was sound.