The Spitfire(s) remained in front line service for less than two decades and it wasn't really the same aircraft by the time the Mk 24(!) came along.
I reckon the Pumas have given the RAF mighty fine service, despite the design shortcomings. There can't be many other aircraft of any type that have retained the original Mk1 status after forty one years.
But at the end of the day, it's all down to money, as always.