I think it's a combination of these two things; the directives about lighting and visual style that come down from production on pretty much every shot seem to boil down to 'more spec, more spec!' and 'can we make this nebula more intense?' Plus, the color grading favored by the cinematographers in s01 isn't doing anybody any favors. But when there's time, as with the pilot or with the battle to rescue the Gagarin, the team still is able to make some really beautiful images out of that, IMO, even though it's not the visual style I'd pick.
There's a noticeable difference between stuff like that and some later stuff in the season like the flashbacks to the Charon and the ISS Buran, and the fact that this stuff is most apparent late in the season (i.e. at crunch time) tells a story. Additionally, one of the things mentioned in some of the interviews about budgeting and delays is that a ton of money went into sets and production design, and I'm not sure if a lot of the EPs had a sense going in of what the VFX were going to cost; most of them just haven't had to do breakdowns on a show of this scale (there's a interview with Ted Sullivan or somebody to this effect, I think from a convention back in late fall). So I wouldn't be surprised if S01's VFX were deeply underbid, compared to the volume of work.
I think that is probably the most realistic explanation so far. The creators of DIS simply underestimated the quanitity of vfx that need to be done
by a mile.
Even with additional money, you
never gonna' make up for such a gross miscalculation. I doubt anyone
wanted DIS's fx look like the way they do. It was just the best result they were capable of delivering under the given circumstances.
Interesting side note (completely different topic, but I'm not gonna' post a third message in a row):
IMO it seems like the late season vfx tried to make up a lot for the previous criticisms: There was still wonky stuff (the Charon chasing the Buran...). But overall,, their approach seemed more "traditional":
We got the first actual beauty shots/establishing shots for our starships. We saw the Discovery at regular warp on the end.
And IMO: Very subtle, but when the klingon fleet approached Earth (
ugh... from a story-wise perespective), they actually tried REALLY HARD to make the fleet look more like "traditional" klingon ships: They chose to put those models most resembling the traditional klingon ship styles in the foreground, even changed the illumination on them a little so they looked like a more traditional main body/nacelles/extended forward bridge combination (No sight of the misshapened "D7" ship). And gave all the klingon starships a more traditional grey hull plating, instead of the funky colored blue/green/yellow surfaces they had before.
The difference was so stark, that I first thought they created new starships. But they just used the most "traditional" looking background ones from "Battle of the binary stars", but noticably changed them even more to fit with prime universe aesthetics.
IMO it wouldn't be unreasonable to assume, that visually, from this point forward, the show will be trying to capture the aesthetics of classic Trek at least incrementally a bit more.