Longer cycle times are more because of less powerful motors and also changes in detergent formulation. When phosphates were removed from detergents they mostly switched to enzymes. Those need more time to activate and do their job, so in my experience the longer cycles also spend some of that time just sitting idle. Letting the dishes sit in a hot steamy environment also helps, kind of like pre-soaking, irrespective of the detergent or spray strength. Using a less forceful pump also means it takes longer to blast away grime from plates, but that works with the enzymes and is also quieter and doesn’t bang around the glasses as much. New detergents may not have adequate time for enzymes to be as effective in older dishwashers, but they make up for it with a stronger spray and more water.
Is it? Never underestimate the amount of energy used by pumps, fans, or compressors, especially ones that run for a while. Many Energy Star labels for instance only report the primary fuel usage of the appliance. So in a gas furnace or boiler, they only report the gas usage. However, they don’t report the electricity usage for the draft fan, blower motor, or circulator pump.* A furnace blower can easily use 1,000 watts, but that’s not factored into the equation. I’m not sure how labels on dishwashers are reported. It could be their own electricity use, their own use plus a range of estimates for hot water usage, or just the hot water usage.
That said, I don’t think the sort of pump used in a dishwasher is as high-power as you’d find in a hot water heating system, because it’s not pushing water through long lengths of pipe. I just don’t know what it is.
*Yes in a hot water heating system the circulator pump is usually separate so that’s not fair, but when converting an old steam system to hot water, the greater gas-burning efficiency of the hot water boiler is somewhat canceled out by the additional electricity used for the draft blower and especially the circulator pump. A steam system likely has neither, or only a very tiny condensate pump, so to do a proper apples-to-apples you need to consider both gas and electric usage, which isn’t on the energy labels.