"70s and early 80s GE had the top rated machines"
Maybe in consumer reports, but there were models that out performed GE. Maytag, Whirlpool and Kitchen aid all had much better wash mechanisms.
Ive used a GSD 1200, and its not the same, yes better than a BOL, but still they were awfully sucky compared to others Ive used. They still have the pump the retains over half a gallon of water, weak shaded pole motor, rapid pre rinses, small filter system in the back that just drains through a weak check valve, pop up tower, high volume low pressure spray, a few large clumsy holes in the wash arm, a paper clip food chopper that usually just snaps off when something slightly hard goes through the oversized course filter. Older GEs also don't do a real thermal hold in the prewash, main wash and final rinse like Whirlpools. GE in the 70s briefly made a machine that had a wash arm on the upper rack and high water change outs to compensate for the water hold over however it seems they abandoned the design quickly even though they would make a machine that good for another 25 years.
Now, a Maytag, Whirlpool power clean module, or Hobart Kitchen aid with a 1/3 or 1/2 HP induction motor, chopper, large active fine self cleaning filter, powerful chopper, and a wash module with many well thought out parts can not even come close to any machine GE has ever made. Even D&M machines that had no filtration still had much stronger motors and even managed to get a wash arm for the upper rack. Even the top of the line machines by GE in the 70 and 80s had the obnoxious pop up tower. They only existed because builders bought them and admitantly they made really really good ovens (they still do) and the filter flos were not bad machines either. But their Dishwashers were always toys, most still are.