You may want to consider that the sound was not due to the DAC (or CD player). The people who recorded music and mastered recordings in the first days of digital were schooled and steeped in the "art" of recording for the RIAA vinyl characteristics. Many were not yet accustomed to working with digital, with its flat response and wide dynamic range. Many CDs, therefore, sounded abysmal. (I had an early digital recording of Bach's Toccata and Fugue in D minor. I forget the artist. The CD ended up being used by my young son for the entertainment of digging in the garden.)
As time progressed, more and more was understood by the "Old Guard", and more new blood, who had fewer preconceptions, entered the industry . Recordings gradually became better.
This had absolutely nothing to do with DACs or digital technology per se.
To prove this to yourself (if you should so desire), take a very early digital recording and a very recent digital recording. Play both on an old 1st-generation CD player, and then play both on a new CD player. You will find out that both CD players sound the same. It is the recordings that sound different.
Jim
hmmm I actually agree with @restorer-john
Have been around since the first Philips CDP. The biggest issue back then was the recording quality of CD's rather than the CDP istelf.
I sometimes think it also was myself so very used to my vinyl player and MC cart that the right sound sounded wrong to me ?
one had also chosen speakers and speaker placement accordingly . I used to laugh at “digital ready” that was a tagline some speaker manufacturers used in the 80’s

but yes I remember some CD releases that never sounded right, to this day there still are some vinyl releases sounding better than digital even with the formats very real shortcomings due to “mastering“ a practice funny enough necessary with older formats to make them work at all ? Not at all necessary with a digital format ?
There are some things you can’t cut on vinyl ? I reckon you make the bass mono for example and don’t let it go to deep to much treble is not really possible either so some EQ was needed to not make the needle jump out of the track .