Great post by GregT- thank you for that.
For my reply to the OP, I will assume we are talking about the top of the line wines and focus the question strictly on what I would call “classic ageability”- or the desire to create a wine that will develop new and special secondary and tertiary characteristics with time, perhaps at the expense of not being as forward in youth.
The wine market at the top end is so large now that you have room for both the “fruit bombs” and the more classically restrained wines.
As I have noted on this forum before, a few years ago I appraised a wine cellar that was included in the sale of a house. It was a large list of CA wines I had never heard of. With extensive research I determined most were extremely expensive and truly mailing-list-only (and then auction in the secondary market) wines. Where critical TNs were available, they were mid to upper 90s with all the descriptors we generally associate with what are usually called “big modern wines”. In the last few years, a whole new generation of micro-wineries has filled out this niche where point score and rarity seem to be the primary drivers that encourage ownership. And as I noted, it is an extremely exclusive market- limited largely to the West Coast and a few cities like Austin with strong West Coast ties in terms of the economic elite.
But also there are many buyers who would like more restrained wines. Not just wines that will age, but will be harmonious with a meal. Aside from wisely learning from and using new technology as it comes available, I think a lot of the wineries that have been like this from day 1- Dunn, Corison etc., are continuing in their current vein.
However, demand is definitely up for the more “classic” wines. Not too long ago you could walk into a high end wine store in Texas and always find a couple of vintages (or more) of Dunn on the shelf. Not anymore. Current vintage only at best. Corison- similar story. Where you used to be able to get the current vintage fairly easily, I have not seen it sitting on a store shelf in quite some time. Diamond Creek and Heitz are also making a comeback. Rarely stocked for several years- now they are starting to be available here again like I have not seen since the late 90s, and they sell through pretty quickly given their price points.
I have also noted a number of newer players which are now faring quite well with a more balanced and long term cellaring approach. It is hard to broadly define the region by it, but among serious wine collectors there is a trend toward appreciation of the general intent of winemaking prior to the creation of the wider mass luxury market.
Now- as GregT noted- Dunn is a good example of a wine that is ageworthy but also quite manipulated. But the fact remains in terms of outcome it is seen as “old school”, and demand for such wines has definitely increased quite a bit in recent years. I think in large part as a replacement to Bordeaux FWIW.
As for direct comparisons with decades ago, that is very difficult. I have only on a few occasions attended vertical tastings where several decades of a wine were compared- and the answer is that even among the most stubbornly “traditional” Bordeaux chateaux there are still so many things that change in that length of time that it is very difficult to look at a younger vintage and say it is likely to come out just like a vintage from 4 decades ago is tasting now. When comparing wines within a 10-20 year period, the comparisons come much easier- though are usually with regard to a specific characteristic or two. When you really look back, though, you will discover the few common threads that make the core of a wine’s long term mission statement- but find it very difficult to think that the young wines on the table are ever going to be very close matches to the mature ones.
(Note, I have only been tasting wine for 23 years- in another 20, my opinion may change as I have the chance to see couple more decades of vintages mature.)