In terms of measurements of course they have and quite dramatically. The trouble is that this almost meaningless from a certain level upwards. From around 2015 to 2021 the measurement became really better in a meaningful way and prices dropped dramatically. Since then,improvements in measurements have become more and more irrelevant to me, as are often outside the range of what is actually audible to us average human.
So today you can get a delta sigma DAC that has excellent measurements and sounds dead neutral for 100 to 150 bucks. If this neutral and analytic sound is your thing, the quality/price has improved by a factor of 5 to 10 depending on your reference DAC from 15/20 years ago.
That being said, nobody can listen to measurements and we all have preferences for some kind of ‘sound’. The best example to illustrate this are products of CHORD which hardly ever measure well, but which continue to well liked or loved by a lot of people because of the sound they generate
If this analytical,dead neutral sound of chip based DACs is not your thing, then nothing much has happened in the last 15 years, I guess, except that the number of available R2R ladder DACs has increased a lot but continue to remain quite expensive (my reference here is the Denafrips ARES 2 which is around 750 dollars, which actually very much an entry level price for this type of DAC )