Rather, what I don't understand is the original argument that roundabouts are bad because the busy direction of traffic has to slow down and gear down unconditi

Rather, what I don't understand is the original argument that roundabouts are bad because the busy direction of traffic has to slow down and gear down unconditionally, whether or not the rare cross traffic is present, so it is then better to have a traffic light there. The "you need power to accelerate out of danger" is a motorcycle argument (and a pretty flimsy one); in a car, you are not gas-pedaling your way out of anything. Your emergency control devices are brakes and steering, that's it. There are moves that powerful acceleration lets you get away with, and they are all reckless, and often built on the assumption that only you have that acceleration. People are now using their high-torque EVs like this. You will never be in a collision close call caused by someone or something doing something unexpected, where the reaction of stepping on the accelerator is the action that saved the day. Can't deny that it could help run from a tsunami wave or fire or something.