That's probably because the episode is not done 100% yet, some stuff looks great, and some stuff doesn't, IMO it's not that it looks worse, it's just that some of the inconsistency makes it distracting. The CG quality is actually better for the shots that you can tell are completed, the little cargo loader sequence looked gorgeous, and you can clearly appreciate not only the better renders, but the improved lighting, if you go back see the lighting on MacF, it looks flat in comparison.
The 2D animation is a clear, clear improvement, I'm also going to say that after watching MacF first EP back to back with Delta, I like the character designs much better in Delta.
The CG for 2008 was very impressive and also why the expectations for Delta are very high, I'll expend on this next.
Yes for the sequence prior to the Aerial Knights showing up, it gets much, much better after that, I hated the presentation shot of the Walkure Valks, everything prior to the Aerial Knights fight sequence looked stiff IMO. Hopefully they'll improve this throughout the series, it's been my main concern since noticing the choreographer from Frontier is not working on this.
I looked at the CG from both first episodes of MacF and Delta, and from what I've seen it seems that instead of going cutting edge for Delta in the way Satelight did for Frontier, the production team has decided to go for volume instead -something they struggled with during MacF. The use of CG on the first episode of Delta is much more extensive than anything in the first EP of MacF, and while the CG for MacF looked gorgeous where it was used, it was minimal in comparison, so there's the trade off. This is actually good thing IMO since it could mean we might get more action per episode than we did in MacF.
As far as the show, I did not like the whole sailor moon thing, it was just too much for my taste, but the worst part IMO is the fact that the music is far inferior to anything that came out of the first EP of MacF if you give me something catchy it'll be easier to get thru the whole sailor moon thing but it wasn't the case IMO, Kanno's work on F is a lot better than anything heard on Delta, not just the songs, but the themes as well. The only track I felt was close to be on the same level as MacF music was the last song used on the episode, and again over the credits. I liked the characters much better in Delta than in MacF though, at least so far. I think Delta has a lot of potential, while not pushing the cutting edge as they did with F, it seems that they are going to be very ambitious when it comes to their set pieces as shown on the third act of the episode.