Ok, so I’ve almost never touched RWBY in my life, I have one episode to my name. So I won’t be speaking about whether or not Ice Queendom is a good or bad adaptation.
However, it does not take a rocket scientist to see how it fails in many other ways.

RWBY: Ice Queendom is plagued by failing animation, dialogue, pacing, and plotting which is downright dysfunctional.

I’m going to address the elephant in the room first: the animation.
If there’s one thing the only episode of RWBY I watched taught me, it's that you don’t need good animation to make a good product. If other parts of your show are high-quality, then it won't matter.
However, RWBY is a 3D show
The good thing about 3D animation is that at least from my understanding, very little can go wrong.
Sure your models can look bad, but there’s no possibility of them changing between shots. Scenes being devoid of motion or boring looking usually isn’t a problem since it's easy to create simple movements to draw the audience's attention. So in 3D, even if everything looks low-quality or rushed, there’s only so much that it can take away from the experience.

But now we’re in 2D, a lot more can go wrong.

And the fact that I’m drawing a comparison between early 2010’s rooster teeth shows to a studio shaft production is a bad sign.

Every mentionable visual blunder is here. Static shots, off-model characters, bad CGI (If I wanted that I’d watch Volume 1), and the blandest backgrounds I have ever had the displeasure of witnessing. Plus they're all reused. Multiple times.
Each mistake takes away more and more from the overall experience, RWBY might work around its visual flaws, but Ice Queendom is completely hindered by them.
Because this is an action show.

AND THE ANIMATORS CAN’T EVEN DO BASIC SCENES

Drawings this poorly done can be brushed aside in shows like Spice and Wolf. The entertainment doesn’t directly correlate to animation quality, but to writing quality.
Action is different, you need sakuga or at least passable drawings to sell whatever choreography you’ve planned out. Unlike 3D, where it is much easier to sell the movements of each combatant (hence why Monty goes crazy with it).

In Studio Shaft's work, each action set piece after episode 3 and before episode 12 are different types of embarrassing. Nothing was smooth or weighty, it was more like stick figures wailing at each other. Every so often impressive sakuga would come out of thin air and wow me, and those scenes are the few that still stick out in my mind. The training battle, the dust shop action sequence, and Yang's battle against Big Nicholas were great exceptions to the status quo.
If only it could have carried over anywhere else.
My heart goes out to the animation team cause they probably went through some form of hell to get this on screens and eke out a full-length production

And I imagine the writers had a similar problem.

PLOT Oh boy does It get worse Starting with some good: As someone who has never experienced RWBY before this, I enjoyed the first few episodes. They may have rushed through plot points at breakneck speed, but it was fun. The animation wasn’t even as bad as the later episodes.

Episode 12 was good as well, a fun little exploration of each of the cast, concluding with a memorable (food) fight scene with good direction.
And above all, the CONCEPTS shown here are solid. The bulk of the plot is inside Weiss's Persona 5-style mind palace, and if it's good enough for P5, it's good enough for an anime.

While the concepts are good, the execution is poor. Ice Queendom’s biggest failure came at the beginning: its inability to set up proper character conflicts. The meat of the show is supposed to be Ruby and Weiss butting heads during their early days at Beacon academy. But by the time Weiss falls asleep for 9 episodes, they don’t have a conflict going. They don’t have anything concrete the writers can work with to create an engaging story. So what’s left is a plot with no focus.

Instead of having meaningful dialogue with Weiss or each other about the conflict at hand and what it means to them, or tackling the main issues at hand, they run around as a series of meaningless roadblocks stand in their way.
Each setback just means another repetition as the characters bang their heads against a wall, the series repeats itself since I don’t think the writers could think of enough situations to fill out 12 episodes of runtime.
During all this, we get a good view of Weiss’s psyche, but there isn’t any payoff for this. By the show's end, I don’t think anybody changed.
And while Weiss and Ruby are incomplete characters, Blake and Yang might as well not exist, they aren’t given anything to do that gives any meaning to their characters. The most they accomplish is being a Deus-Ex-Machina for the final obstacle in the dream world.

If there is one high praise I can give this mess of a story though, it's that it was fun. Yeah, each plot point felt like meaningless filler, but it was engaging filler. As I said, the concept itself of Weiss's mind palace is quite good. And much like a Persona 5 dungeon it was filled to the brim with over-the-top symbolisms about Weiss' inner feelings, so much so that It continually piqued my interest. Such as when a small army of 5-year-old Weiss' escapes out of the “Sillies Prison”, grows 10 times their own size, and starts walking around destroying everything.

For a brief moment, I felt like I was watching Attack On Titan, complete with over-the-top twists. (If only they were good twists though).

So as the trash fire burned, I sat back and watched with glee as more bullshit blazed on. The worse it got, the more fun I had. I could rail on Ice Queendom for many more pages but It wouldn’t be true to the experience I had.

Above all, I just wanna watch some normal RWBY now.