TL;DR: it fell off.
A lot has changed since volume 3. The biggest change, in my opinion, is that RWBY has become a dark, story focused anime instead of a lighthearted fighting series. This made it much worse, as it excelled at the humor/fighting but did not excel at writing. Beyond that, these are the changes worth talking about:
The RWBY team was split up, which was a massive mistake, as it forces the story to narrate four different sections of the story at once, making the plot progression very slow relative to the episode count. Fortunately, they reunite later in the story, so this is not as much of an issue as the series goes on.
Lots of new characters were introduced, including Oscar, Salem and her henchmen, the reaper, and the Spring Maiden. This lead to a bloated cast, which is especially frustrating given the new characters were mediocre.
Monty Oum (animator) died, so the fighting scenes got worse across the board. There are still some reasonably good fights (e.g. Qrow vs Tyrian and the final fight in V4, ___ vs Cinder in V6), but the decline started to set in pretty hard after V5.
After a certain episode in volume 6, RWBY now has a… somewhat conclusive main story?
Beyond this, I have some comments on the individual volumes. Volume 4 was mostly fine — I was actually quite surprised that RWBY had some good fights in it even after Monty’s passing, but this seems to have been a fluke, given the fights were so poor in Volumes 5 and 6. Beyond that, there isn’t much to comment on here, given that the story was too split up to progress.
Volume 5 was atrocious. It was so bad that by the end of it I felt sick, mostly because of how horribly it ended. The main problem with this volume is the script, which leaves me with lots of questions:
Why does Sun run off when they finish dealing with the White Fang?
Why do they all stand around like retards when Weiss gets impaled with Cinder’s spear?
Why don’t they conveniently get rid of their worst villains (Cinder and Adam) when the plot is naturally set up for them to die or go to jail?
Why do they go for such a serious tone when they fail so badly at it? At its peak, RWBY is a cringey/light comedy with cute fighting scenes.
Why do they have to divert so much screen time to the faunushit? That subplot didn’t work in the first volumes, so I don’t see why they should have to force themselves to double down on it. It really shouldn’t be too difficult to make up some plot convenience that compels Blake and Sun to travel to Mistral earlier in the volume to help RNJR.
Volume 6 was somewhat better as they actually developed the main plot with the Jinn drama and the writing was no longer as horrible. Wasn’t particularly enjoyable, but it was a large improvement over volume 5.
Until now, I would score the individual volumes as follows:
V1: 7, V2: 8, V3: 7, V4: 6, V5: 2, V6: 6
scoring:
Design (15/15):
Distinguishment: (5/5)
Animation: (2/2) - improved
Sound: (2/2)
OST: (2/2)
Character designs: (2/2)
Backgrounds: (2/2) - improved
Script (33/50):
Character Investment: (10/10)
Character Realism: (1/2)
Character Complexity: (1/3)
Plot solidness: (1/5) - volume 5
Plot complexity: (3/10) - volume 5
Ending: (4/5) - fine, i guess
Pacing: (4/5) - not notably bad or good to me
Stakes: (9/10) - high stakes
Value (6/15):
Thematic elements: (0/5) - stop forcing the faunus shit
Skill: (1/5) - miles and kerry, man.
Originality: (5/5)
Enjoyment (7/20):
Did I like it: (7/20) - narrative is overrated… until you watch volume 5.