Honestly, carbs have been around long enough that all the real nits were worked out...until the EPA stepped in...leaning out the mixtures, strangling the breathing, squeezing manuafacturers get every bit of power out of a drop of fuel...yet lower emissions and provide a "driveable and efficient marketable machine..."
HD R&D all the while is desperately trying to regain the lost horsepower, upping displacement, infusing more precisely metered EFI, working in concert with ECM (Electronic Computer Module) multitasking a host of sensors to monitor engine loading, throttle position, spark advance/duty cycle etc into the mix, reducing rolling resistance and tire technology as well...IMO they have done quite well considering the uphill battle. Most other manufactures totally change their engines and running gear every 4-7 years...HD somehow has keep things together for what...20-30 years regarding the basic engine and running gear? Pretty incredible when you think about it.