The major factor in the development of early dishwashers was the detergent dispenser. Without a dispenser, the first fill had to be the only wash and the water in that fill was not hot enough to do all that it needed to do. KitchenAids were particularly deficient in this aspect. So getting an electrically-operated detergent dispenser was a huge factor in performance because it allowed one or more fills that could be pre washes or rinses to heat up the machine and the dishes before the main wash. The cooler water in these periods also helped deal with protein soils that were easily cooked onto dishes if hit with super hot water. Another factor was the development of a non-sudsing surfactant. Early dishwasher detergents were various phosphate formulas to soften the water to prevent hard water deposits and make it more likely to remove light soils, but it was half of the needed partnership. After non-sudsing surfactants were found, the search for a stable form of dry chlorine was needed to not only help remove stains, but also to help breakdown organic matter. A very good detergent is very important in machine dishwashing.
Some machines needed more preparation of dishes before being loaded. Some had filters to deal with food particles, although not the really fine ones. The early GEs, with the timer that was run off the main motor could not stop the impeller to drain so instead of food soil being able to settle out and go down the drain, the impeller kept throwing water with food particles until there was so little water that it was below the impeller and a lot of the tiny particles were stranded on the dishes. The cycles in early dishwashers were short so heavy soil could not be thoroughly washed away, but if the user had the inclination, the machine could be used to pretreat pans that could then be more easily washed by hand. Machines with a separate drain pump usually had a small strainer that caught debris so if dishes were not cleared of food before loading, that would need cleaning from time to time.
Your sentence, "Not those vintage KA, GE, WP's etc. that have a good record, but odd ones like the Kaiser water powered, Apex, bow tie impellers, and those odd designs." reflects some misunderstanding of the brands and designs because you say, "not GE" but then mention bow tie impellers as one of the odd designs when that was one of the most effective impellers, not only because of the shape, but also because the stainless steel did not chip or lose its sharp leading edge like so many Bakelite impellers did and that impeller was attached to a pump that was very effective a grinding food particles and thoroughly pumping out the machine. At the end of each drain period except the last rinse, the fill valve was activated for a few seconds to help flush food particles from the pump chamber.
Modern dishwashers feature many improvements like random loading and water supplies for each rack, but it was possible to get very good performance out of many older machines if you removed heavy food soil, loaded the machines carefully and ran them immediately after loading before the food soil could dry, but you can see the pitfalls of that formula in today's housekeeping practices.
