Ok, how many years back that limit was reached ? What was that limit ? How that limit was decided ? If all modern dacs are beyond that limit then does that mean all dacs should sound same ? If not then what are the factors for creating the difference in sound ?
1/ Ok, how many years back that limit was reached? 10 to 20 years ago.
2/ What was that limit? 16/44100.
3/ How that limit was decided? ABX testing, initially the DSD vs CD PCM debate. Later, comparing to 24/96000 to 16/44100.
4/ If all modern dacs are beyond that limit then does that mean all dacs should sound same? Yes.
5/ If not then what are the factors for creating the difference in sound? Jitter. Choice of anti-aliasing filter, for younger ears than mine. Poor recording technique, some DACs have more headroom to deal with inter-sample overs. There will be other reasons.
Some of what I have said is contentious. Amirm has written some good articles on how you can learn to pick differences. If 16/44100 is borderline I would say 24/48000 is very defendable. For me, having the latest DAC gives me a nice warm glow ergo, it must sound better. Well, to me at least.