The word "classic" in movie, style and art means timeless and lasting.
Timeless and lasting normally means good, that's why we reproduce them.
"Classic" in reference to cocktails are lazy drinks that any bar can make, that's why we keep reproducing them.
Whiskey sour is just a lemonade whiskey, let's not kid ourselves here.
If we want to make actual good drinks, I think we need to re-evaluate what good means. Instead of holding unearned deference to "classic" drinks as good, and trying to replicate/refine "classic" drinks