I hate the current art direction so much - everything is so industrial and vanilla with no color.
Same. That's one other reason I really dislike Kenneth Scott work on the Halo serie (since he was an excellent art director for DOOM) and what he brought with him before leaving (while I'm glad he left the company btw).
They tried to give the human facilities and style a very clean, rounded, big and sanitized look while making the Covenant very organic, both with the shapes and the technology.
While I understand why they wanted to do this, they, in my opinion, failed to keep what Halo established for years, having a excellent blend between mechanic shape and natural structure, with a retro-futuristic kind of style. What I like for the art direction was that, even if it's in 500 years, the style make like it could happen tomorrow, making it a not-so-far distant future. This is now lost... (Well, at least, I got some pleasing art with Halo Wars 2.)
And it starts from the concept art step:
Taking a look at both concepts, if they didn't have a logo on the bottom, I couldn't tell which one was from Halo or DOOM. Could you?
And when I look at Bungie human style, it's way more grungy, not so clean and sanitized:
And the first one is even not from Bungie, it's from Certain Affinity for the Defiant Map Pack from Reach, yet they kept the style Halo always had.
The one thing which burns me it that 343 doesn't seem to want to move from this art direction, but they had no hesitation to ditch the old and classic one...
Plus, I don't like how they keep increasing the specular on their structure and 3D models, increasing the sanitized looks...
What don't you like about it? They're modelled so as to be the precursor archetype to flood. They fit perfectly in Halo because they're based upon classic Bungie designs, and already seem a lot more compelling than any 343i era enemy-designs thus far - not that that's saying much.
As I said, I don't like 343 going full organic shape for alien species, it wasn't really a thing for Halo, maybe apart from the Flood, and even when the Flood were, by nature, organic, they didn't had such organic shapes.
I don't mind the Precursor no being bipedal, that's quite cool to see something new, but you know, I guess it's just personal taste at this point. I'm not a huge fan of organic shaped characters, the one exception may have been Mass Effect because it perfectly suited the universe they were in.
And also, I don't like how everything 343 designs is meant to be frightening. To be honest, I would have make nightmare when I was a kid if I played a game with every characters having teeth like the Guardians, the Promethean Soldiers, the Halo 4 Flooded Spartan form, etc...
And for the lightning and the neon aspect, I think this picture show everything I could ever said about the design approach from 343 compared to the classic one: