But what you seem to forget is that we're not talking about 7 or 8 which were feature loaded releases with no promises of performance improvements. We are talking about 9, a release that is semi devoid of new features, but had significant promises in improved performance and stability.
And personally I do remember the early days of both 7 and 8... Well actually I remember the early days of 4,5,6,7,8 and of cause 9. 9 has been the worst out of all of them for me. I can cope with slow releases if there are a lot of new features. iOS 9 feels like iOS 6 in terms of feature, however, iOS 6 performed better than iOS 5 on my 3GS and a iPad 2.