TMA is busy and complex, I agree, but it is completely different from enroute controlling so they can't really be compared I'm afraid.
I've known valid people come from TC and fail to validate in enroute so how can it be that much easier? Nothing to with the training regime either.
TC=point at each other and expedite
AC=solving conflictions within a 10 mile airway whilst traffic is almost head on at 1000knots closing speed.(not all sectors)
I've seen DTY, for example, shift 67 aircraft in an hour. Yes, maybe not overly complex, but a lot of RT and not much room to play with as at least half were coming out of the cruise so doing over 400 knots ground speed