There is no single, simple answer to these questions. Some new drivers and technologies are quite good, though not necessarily better than all that preceded it,, and a lot of older gear/technology has stood the test of time. My all time favorite midrange driver is a horn compression driver made around 1939. I can also think of a number of older woofers that are pretty hard to beat in certain respects. There are some vintage parts for crossovers that are still sought after for making modern speakers.
Buying used vs new speakers from a technology perspective
Do you believe a speaker's components like drivers and crossovers can become "outdated" for lack of a better word? For instance say someone is selling a pair of speakers that cost $10k in 2008 for $5k now. Comparing that speaker to a modern day $5k new speaker only looking at driver design/drivers, cabinet construction, crossover components/layout and other materials what kind of technology gap are we looking at?
Have there been technologies or designs that have come out in the past few years that you couldn't live without after hearing?