DS4 is supposed to be premium I think
It is over its own Stellantis group cars.
My take is premium cars have better soft touch materials and more of it in the cabin along with the tendency to find better materials such as seating and switch gear tend to have more dampening etc. Doors tend to shut with a more reassuring clunk and the likely hood of better sound deadening etc. None of this though distracts from the interiors of say less premium cars such as the Sportage which has one of the best looking interiors especially on the scheme. I also feel the gap is closing between what we would class as premium and a non premium cars.