'with a few exceptions such as Zambia'
I'd agree with you based on my time there in the '70s but, I believe, things have not been so good recently.
Corruption is one of those continuum problems. It's not this or that.
If you and I are at a meeting and I buy you lunch, am I trying to corrupt you? If we go to the best restaurant in town, is that corruption? If you can't afford to come to the meeting and I pay for your travel because I value your contribution, is that corruption? If your employer insists you take unpaid leave so I pay you your equivalent salary, is that corruption? If you tell me you're thinking of voting for something I disagree with so I say I'm not sure I can keep paying you, is that corruption?
I think most people would answer 'no' to the first question and 'yes' to the last but where does the switch happen?