Barnes said the Springbok style was too concentrated on winning by stripping the game back to its barest essentials in his Times column.
That was evident at the weekend when the All Blacks put on a 'kaleidoscopic display' to beat Australia, while South Africa had been 'too parsimonious' in beating Argentina.
"It's easy to see the All Blacks as the sport's saviour against the muscular conservatism of the Springboks; easy but erroneous. As a former player, I have immense respect for the heart, spirit and commitment of these Springboks.
"As a fan, however, I hate to see how they are stripping the international game back to its barest essential when they have so much more to offer in the way of talent," he said.
Barnes said what South Africa's director of rugby had done in playing limited rugby made perfect sense – if winning was the be-all and end-all.
Since coming into the role as Springbok coach Erasmus' side had played attacking rugby but found themselves unable to cope with the All Blacks' attacking game.
"Defence became the focus. It still is, with territorial control a crucial component against their rivals. In the South African rugby mindset, if they can beat New Zealand, they can beat anyone. The record stands up to scrutiny," he said.
"To be not necessarily the best, but to beat the best South African rugby has taken a step backwards. New Zealand have long been heading the other way.
"Between the death of amateurism and the birth of the professional era, the Kiwis transformed their game into something slick and entertaining. New-look New Zealand were born. Their win record is remarkable.
"The capacity to take the game to unprecedented levels is likewise off the scale. The 1987 World Cup winners, the 1995 losing finalists, the 1996 winners in South Africa and the 2015 world champions all rank among the greatest Tests teams the game has known," he said.
Yet Barnes claimed there was cynicism in New Zealand's defensive method when killing attacks five metres from their line, and that was apparent in Saturday's win over Australia.
That would have been noted by the South Africans, Barnes said.
"Fingers crossed that these teams are playing for the title when they meet. The clash of cultures promises to be something special.
"If New Zealand are able to recycle the quick ball on which [halfback] Aaron Smith thrives, the 'good' guys with their naughty habits will be spectacular. If the 'bad' guys – with a defence designed to slow even the All Blacks down – wear down the men in black, it will be a triumph for ruthless planning and absolute power," he said.
The All Blacks are scheduled to play South Africa in the 100th Test match between the sides on Saturday 25 September.