I would suggest that the whole discussion here is an illustration of us not doing classical music well. Previn wanted to make it popular and was excoriated for that.
I'm not sure anyone here certainly is excoriating Previn for his desire to popularise classical music, including his decision to appear on M&W. Certainly not me - I think it was a great opportunity, a smart move on his part to agree to do it and it is a great sketch. My point is that we shouldn't define his career by that performance and that is most definitely isn't the high point of his career (although it might arguably be the high point of M&W's careers).
In part that was the genius of the sketch -
In a weird way that so many in the UK still see Previn defined by that sketch demonstrates, sadly, that he actually failed in his attempt to popularise classical music. If people see that sketch as the high point of his career then all he achieved was to make himself very well known in the UK, rather than to make classical music more accessible and well known.
Actually, in my view, Music Night was much more faithful to the vision of popularising classical music and more pioneering - the notion of a conductor and an orchestra engaging directly with an audience on prime time tv and focussing on serious classic music in a serious (albeit unstuffy manner), was revolutionary. And for that we need to thank Previn's fellow traveller on that vision, John Culshaw. And he deserves thanks too for being visionary enough to agree to ask Previn on Ammond's behalf to do M&W and to be the person who gained his approval. As custodian of Previn's Music Night contract he'd have been perfectly within his rights to say 'over my dead body - I'm protecting the image of my star and my programme, no way is he going to made to look stupid on a comedy sketch'. But he didn't.
Sadly Culshaw died earlier and younger than even Eric Morecambe.