Props too, look at the Enterprise D in 4k and it looks way more fake than it did on the old CRT. The blemishes that give it away blur together to make it look way better on screen. Watch Adam Savage's Tested - The Next Generation Filming Model! if you'd like to know more.
The sets look worse too; on the blu-ray discs you can see shit like screws holding the consoles together, dirt on the floor, scuff marks on the edges of stuff from the actors' shoes and such.
Funnily enough Voyager can't get a similar remake because it was shot on tape, so the masters are 480i and that's the best you're going to get.