Why have capacitors improved so much over the years?

I am not sure the best capacitors today vs 15-20 years ago are in fact better. It seems to me there is now a market for high grade fancy capacitors in the DIY hifi community, and so there are some smart companies who are riding that wave and marketing to that audience.

Dueland, for instance. It would be interesting to hear from people who have been in the high end hifi manufacturing business for a long time, hear their commentary on this. There seem to be some others on this forum who will do modifications to some gear for a fee, using these fancy branded caps and other components. Things like salt used to just be salt. Now there is Himalayan salt, Moldon salt, etc etc. It is still just salt, and before there were better quality and worse quality salt for cooking, the marketing business just had not latched on and did their thing.

I had my amp recapped 10 years ago with 60s era NOS Aerovox caps one of the best and cheapest upgrades I've ever done. So better technology maybe, better sound maybe maybe not.

If they have, and I wouldn’t doubt that they have, it is likely due to more precise computer aided design and robotic manufacture.

I've been modding for perhaps twenty years now, IME, both film and electrolytics have improved, I presume for all the reasons above. Really, very few choices years ago with boutique caps, most were general use variety. As I recall, the first audiophile grade film caps I used were from VH Audio, Duelund, Jantzen, Mundorf, seems like they all came to market in about the same range of time. So many brand choices today, way more values, voltages, metallurgy  available today. I've yet to hear a bad boutique film cap in my mod projects, only sq issue has been less than preferred colorations, large physical size sometimes makes fitting a chore.

@troidelover1499

It is still just salt

not sure you'd have a lot of chefs and gourmets in agreement... 

@jond - NOS capacitors, huh? Uh oh, another crazy rabbit hole!