Whilst there are certainly many CC's which are delicious and approachable young (witness the indecent speed of disappearance of the 2015 Riecine I got from TWS last year) there are absolutely plenty of them that benefit from extended ageing and whilst one man's 'improved and more nuanced and complex' is another man's 'different to how it was before and I now like it less' I have been lucky enough to enjoy a whole host of CC's with significant age that have been really stunning, some of which have 'no right' to be such as a Rocca delle macie 2001 basic last year, a badia e contibuono 1985, a riecine 1988 among many others. Vintage is certainly important as is producer of course and classico does suffer from having a huge number of frankly bog standard producers who qualify simply by being within the boundary. The consorzio have tried to ameliorate this with the introduction of Gran Selezione, but if you talk to producers like Montevertine you realise that the requirements introduced to qualify actually move the wines further away from where they should be as a true expression of the grape and the terroir. Of far more interest to my mind would be a classification based on geography and a grading of the vineyards/estates in a Bordeaux or Burgundy model which would more accurately reflect the differing styles within the region, allow for a degree of difference in overall grape blend and regulate ageing. Of course the smaller producers are in favour of this but the real powerhouses would have much less of an interest as many of their wines would be classified low down any order.
Of course we were originally talking Rufina rather than classico and there are to my mind more examples of Rufina that are younger drinkers than classico but with a couple of notable exceptions, Selvapiana being one and most especially with Bucherchiale. Sangio in hot vintages can, with age, tend towards the stewed so it's certainly not a hard and fast rule to say that it ages, certainly plenty that do not ( a castell n villa 1995 springs to mind as do, sadly a fair few 1997's that ought to have been better). As many winemakers have come to realise globally, acidity plays such an important role in making ageworthy wines that really hot vintages in Tuscany skew the balance too far away from it and result in immediately delicious drinking with little future potential.