Not true.
South Africa didn’t even compete in international rugby from 1984 to 1992 so I’d say that was a considerably lower ebb for them.
They were absolute dogshit from around 2001 to 2003 when Rudolf Straueli was coaching them and bringing them to army camps and such.
When Jake White took over after the 2003 World Cup, they were suddenly revitalised and won the Tri-Nations in 2004 and would go on to win the 2007 World Cup.
They’ve just had a similar coaching change. However even since the 2015 World Cup and under a lame duck coach they’ve shown they can mix it with the very best on their day. Under a proper coach in Rassie Erasmus, they’ll be a serious force in 2019. Never underestimate the resilience of South African rugby.