The main thing that has inarguably improved over the past couple decades is the fabrication processes by which monolithic ICs are made - and since the overwhelming majority of audio DACs are based on monolithic products . . . the palete of resources available to the IC design engineer has changed considerably.
That being said . . . just as everything else in audio (and life in general), the success of a design is very closely connected to how the designers/engineers work to reach their goals with the resources they have available. And in the late-1980s/early-1990s, the goals of most IC designers were probably more similar those of audiophile products than they are now -- there used to be many $10-and-up "statement" mono DAC chips available, that cared nothing for power consumption or single-supply operation, and assumed that the circuit designer had no problem spending extra money on separate circuitry to do the processing/upsampling.
Nowadays, a $4 audio DAC is VERY expensive, they're all at least stereo (if not multichannel), and have some sort of oversampling or sample-rate-converter built in - making the circuit designer's job much easier, if they want "off the shelf" performance. Most of them are also much more flexible in terms of software control, and place low power consumption as a priority. Translation: these days, the perfectionist audio business has very little part in paying the bills at Texas Instruments et. al.
It's true, the chips HAVE gotten "better" . . . especially if you're paying attention to the same parameters that most IC designers have. But all circuit architectures have their stregnths and weaknesses - and they're all ultimately dependent on the designers and engineers of the final product whether the parts fulfill the promise of what the chips themselves can do.
That being said . . . just as everything else in audio (and life in general), the success of a design is very closely connected to how the designers/engineers work to reach their goals with the resources they have available. And in the late-1980s/early-1990s, the goals of most IC designers were probably more similar those of audiophile products than they are now -- there used to be many $10-and-up "statement" mono DAC chips available, that cared nothing for power consumption or single-supply operation, and assumed that the circuit designer had no problem spending extra money on separate circuitry to do the processing/upsampling.
Nowadays, a $4 audio DAC is VERY expensive, they're all at least stereo (if not multichannel), and have some sort of oversampling or sample-rate-converter built in - making the circuit designer's job much easier, if they want "off the shelf" performance. Most of them are also much more flexible in terms of software control, and place low power consumption as a priority. Translation: these days, the perfectionist audio business has very little part in paying the bills at Texas Instruments et. al.
It's true, the chips HAVE gotten "better" . . . especially if you're paying attention to the same parameters that most IC designers have. But all circuit architectures have their stregnths and weaknesses - and they're all ultimately dependent on the designers and engineers of the final product whether the parts fulfill the promise of what the chips themselves can do.