Having just flown SA from LHR to CPT via JNB and return in J, my simple observation would be that there are legion little things management could do to improve the overall experience- such as introduce consistent standards, whether in seats, service or ground support. Basically SA struck me as friendly chaos with good food and wine. Traveling on three widebodies we had three different seats, with the most comfortable beds reserved for the domestic hop. Service was uniformly friendly and shambolic. JNB was organised chaos: a domestic transfer required a further security check and four passport scans. Both the CPT and JNB lounges had half their coffee machines out of order.
I liked my trip on SA but it became obvious very quickly why it's losing money and market share.