I will never get the hang of opera blogging. I can't rant on endlessly comparing Kiri to Renée or Anna and Maria.
I spent a lot of time in the 80's making music on computers in conjunction with synthesizers and know exactly how easy it is to achieve the perfect trill. I would make the trill in Cakewalk and then copy it around wherever I wanted that effect, transposing it up and down. All my trills were perfect. So what? Perfection is boring.
Any singer you can name is sometimes bad, sometimes boring. Well, maybe Maria was never boring. You might wince at her wobble, but you would not be bored. Kiri was capable of the sublime and the pedestrian. Cecilia does not discipline her legato. Anna is capable of just blasting meaninglessly away and doesn't try for subtlety in her more intense singing. Renée is a crossover and can't help it. All have feet of clay or are not worth listening to. You pick.