I haven't really followed the behind the scenes story on the production after Monty's death, despite consuming a fair bit of RoosterTeeth production/meta-entertainment content over the years. But I think it is fair to say that the obvious drop in quality subsequent to Monty's death was of course also fiarly inevitable. But I always got the impression that while Monty certainly set the thematic tone and overall creative direction, both the production and the story were nearly as heavily controlled and influenced by Miles Luna, even at the beginning. And unfortunately, even from the start the show had problems in the story department--they got worse after Monty's death unfortunately, at a time when it needed to be reaching to a higher level.
There's a couple of reasons for this. One, the show has always had a kind of identity crisis: it was clear that at the beginning it was supposed to be a sci-fantasy version of what Monty gave them in the seasons of Red vs. Blue that he had worked on as head animator (or perhaps better said, the animation department--the man was an utter machine by all accounts and evidence I saw over the years). But everything Rooster Teeth is more than a little bit camp, and the show had really predictable, cliched and outright tired writing from even the earliest seasons; I used to have a hobby for a couple of months where just before the weekly episode would drop, I'd go on to a forum or discussion page somewhere and predict the entire breakdown and flow of plot beats and character interactions of the forthcoming episode just based on the setup from the previous one. It was disappointing how precise one could get.
But it was initially buoyed by Monty's unparalleled artistic eye in the design and animation, including, especially, unbelievably creative action pulling from as wide an assortment of influences as anyone in his profession has ever synthesized into their own unique and eclectic brand of action and fantasy martial arts choreography. I really think that only maybe Legend of Korra and a handful of high quality films like Sword of the Stranger can compete with what he was capable of producing as a regular matter with a fraction of the resources. And as a great bonus, charming physical comedy too. I almost bust a gut in that early first season episode when the hunter initiates get springborded into the air and everyone turns into a sleek aerodynamic missile...except for Jean who flips rapidly end-over-end around his center of gravity as if he were a figurine imbued with too much spin--classic!
But even a team of decent animators who got to learn directly from Monty couldn't make up for his absence and thereafter the show just descended into above average action animation--it's probably fair to say none of it would feel that disappointing if not for the absence of Monty's work that you can feel while you take it in. The action has definitely had its moments here and there since, but it's not enough to keep me invested for the ride with the story as it is. The show turned out to be a hit with young girls as I understand it (perhaps not surprising given its lead female cast, consistent female empowerment generally, and it's aesthetic), and it seems as if they chose to tweak the formula a little to capitalize. Which is perfectly fine--its not like it had landed on it's tone and voice yet at that point anyway, if you ask me--but dialogue continued to be soapy and melodramatic, the overall story (from what I've seen) is still kind of a paper-thin pastiche of pop-fantasy tropes, and the direction and voice acting is...let's say mixed.
So I've only watched a 1-4 episodes per season over the last few years. It's fine, I suppose. A little candy-apple and paint by numbers for my taste, but you can't deny that they put still put a lot of work into their art design and animation, running with that look that Monty established for them. And the music is pretty boss too: even with sometimes saccharine/melodramatic lyrics, that rock-meets-thematic-meets-neodisco-meets-pop sound that Jeff and Casey Lee Williams have landed on in so much fun, so unique, and such a perfect compliment to the tone of the show. But when I'm watching it, I just can't help but think of all the years of brilliant, unparalleled animation fight choreography that we've already lost in the years since The Man died far, far too young.
Edit: Wow, I have to walk back some of what I said above; I just decided to give RWBY Volume 7 a try the last few days, and as it turns out, it is certainly the best season from a storytelling perspective and the best in terms of action and artistic vision since Oum's death. The show has finally really hit its stride and the writers and directors seem to be figuring out how to tell a story like this: the plotting and dialogue is a huge step up, as are the performances from the principle cast--even those who were previously weak links. The tone is significantly more weighty and not just "dark" in the melodramatic quasi-edgelord manner to which the middle seasons were prone. Character dynamics feel real and loaded with mostly realistic emotional subtext, things are much less predictable and plot holes are more scarce--as is the general sense of vaguery that was so often needlessly present in earlier seasons because of a poorly framed and structured back story: we more or less know all of the principle players behind the scenes now, the stakes and the rules by which the world operates are more clear, stable, and refined, and the story is better for all of this.
The music continues to excel: Neopolitan's new theme is just so good; usually a song with lyrics that on-the-nose would make me feel like it was a guilty pleasure to enjoy it, but I can't even be bothered to burden it with that caveat--it just pumps the blood. The non-lyrical score is also more nuanced than it has ever been, with many very subtle variations on returning themes that effectively twist the feeling of critical scenes in effective ways. The animators also seem have to finally gained the experience to start to truly do a decent homage to the style Monty left them--there are some battle sequences here that I think he would be truly proud of. I'm seriously back on board for this ride in a way I haven't been since the earliest episodes--they've turned it around that much.
Oh, and (trivial bonus that it may be) everybody gets brand new designs this volume, some of which I think may be fertile ground for CaS!