I agree with NS, bass is the only place anything has advanced, and then not in an absolute way, but in a way that allows us to use smaller solutions.
For bass, the improvements have come from driver design, amplifier design and DSP. Modern top of the line woofers are pretty amazing, and while they can be equaled with vintage drivers it takes a lot more of them, or a bass horn. Of course we're only considering the best implementations as modern bass can also be seen as the kind of sound you expect from auto SPL competitions... so , not that... But for example, I have compared an excellent modern 15" woofer, the Acoustic Elegance TD15H+ with JBL 2226 and even AE's version of a vintage driver, the 15M. The H+ is a bit less efficient at 94 dB instead of 99 dB, but it sounds much cleaner, there is a lot less measurable distortion and the woofer can play a lot lower as well. Modern class-D amps like Hypex NCore series have an iron grip on the woofers, and DSP allows us to omit a passive xo and use room correction, a large benefit with bass. Done right, a single AE TD15H+ can produce very high SPLS, very low distortion and sound extremely "fast", no problem integrating it with single driver, horns, etc that are often difficult to integrate other drivers with. It has 38mm peak-to-peak Xmax vs just a few mm for most vintage drivers, and power handling is much higher too... there are huge advantages to surface area over excursion but some amount of both is ideal for most of us who don't have space for bass horns or a dozen woofers in their listening room.
While there have been advancements in dynamic driver design I'm not sure they have actually exceeded the sq of vintage systems wrt to mid/high frequencies. It is true tweeters have gotten much better with ribbon and Be domes, but they aren't as good as CDs/horns anyways...
