Remastering also brings in color gamut issues and resolution issues. Most television at the time was shot on 35 mm film. You have to make different color correction and contrast correction choices when remastering for modern televisions. The "red" command uniforms in Star Trek: The Next Generation are actually fuchsia. All the processing decisions made during shooting and video transfer back then were made with certain assumptions in mind.
Yes, I've seen the comparison shots in which people have pointed out that you can now see the woodgrain and cardboard in the 24th century sets and props. One of the fascinating things before any of this was really a big thing was getting books about the production of such series and seeing pictures of the props. The hero props with moving parts and working lights look great, the others... not so much. But they didn't have to be because they'd be seen in long shot for a few seconds at a time taking up about 0.5% of the overall screen area, so crude construction and paint jobs were adequate.
I remember a big fuss about colour balancing issues on the release of the Doctor Who story 'The Invasion of Time'. TV production in the 70s was typically a mix of video in studio and film on location (more or less but we won't get into the minutiae!). When they came to release this story on DVD the colour balancing of the video and film sequences resulted in one character's robes appearing to change colour depending on which room he was in, being purple on one and red on another. Same costume, different colour effects of the media which were not fully accounted for in the remaster.
This has also bled into recent colourisation efforts for black and white Doctor Who stories. The TARDIS console room was always described as a 'gleaming white' futuristic control room. In monochrome TV production, white was about the worst thing it could be because it would just flare on the cameras. So they would design the sets with colours that would
appear white on the screen. The TARDIS console in the 1960s was in fact very pale green. They never bothered re-painting it when it appeared in the first few colour seasons so the true green colour was there on screen for people to enjoy. We also uncovered a plethora of colour production stills from the time which showed the floor of the set to be blue.
So when they came to colourise some of those old stories, they've been colourised to match the reality of the sets rather than the intention of the producers. While the technical aspects of the work are superb, I do think that might have been the wrong choice.