The thing about Murders at Karlov Manor is that from a story perspective, it couldn't have been set anywhere but Ravnica. And it especially couldn't have been set on New Capenna.
The story of Murders is ultimately about the fallout of March of the Machine on both Ravnica as a city, and on Kaya personally. The motivations for the high-profile deaths that litter the set are tied directly to elements of the Phyrexian invasion. The manner of murder is specifically set up to overcome the barriers Ravnica as a setting provides to a murder mystery. And Kaya only gets involved because of her questionably defined but always present relationship with Teysa Karlov.
Ravnica also comes pre-built with a host of established characters, who conveniently all hate each other. This enabled readers to theorise about whodunnit, as each daily chapter provided more information and more intrigue. People considered all kinds of threads: Could Jace be involved? Might Azor be pulling the strings somehow? How does Judith plan to survive her crazy plan? Lazav?? By the time Proft said "I know who the killer is", you too could get it. (then for some reason they delayed the reveal chapter so they could reveal the killer in a spoiler stream. even when the story is good, the management is bad)
If you move the story out of Ravnica, the whole thing falls apart. You lose everything that makes it work. A new plane would be functional, but a lot less engaging. Fiora is about political scheming, even more so than Ravnica. And New Capenna...
New Capenna is not a particularly well constructed setting. It works as a sparse background for a Magic set, but when you start poking at it, it falls over. Like, one of the nicer ways to describe New Capenna is "discount Ravnica", because you are comparing it to one of the game's most successful settings. And that's what New Capenna is - a city controlled by a number of distinct factions, built out of specific colour combinations. But the New Capenna factions are not as good as the Ravnica ones (and the Obscura are literally just the Dimir). There is crime on New Capenna, but there is no authority against which that crime is committed, which makes things rather hollow. Ravnica, as strange as its laws are, has laws, along with people to enforce them. (note: I am aware of the Doylist reason why New Capenna has no police. Watson is still crying.)
Ravnica being well-developed allows it to function as a backdrop for a different idea. New Capenna's issues do the opposite. In fact, any return to New Capenna would need to reckon with how the setting got completely turned over by the return of the angels. You can't just say "well the crime has punishment now, onto the mystery". You have to actually engage with the big change, or you're just dragging New Capenna into a deeper hole.
conclusion: When the Magic story is good it's because the writer looked at the setting and characters they were given and used them together well. This is only possible if you have a setting and characters that can be used well. Ravnica has that, the crime plane does not.
These are all great arguments for why if you wanted to make a murder mystery film and set it on one of the Magic: the Gathering worlds, Ravnica may indeed be an excellent choice. But this is not the same thing as creating a set of collectible cards that convey the mood and sense of a murder mystery— which is why I think this set is a horrible mess.
The thing is that you could make it work in a narrative form: in a narrative you control what the audience sees and when. You can make it so by the time we see the bits of the setting that look like a modern police procedural, we’ve forgotten the parts where it’s a 1920s Agatha Christie story, or a late Victorian Sherlock Holmes story, or a Ravnica story. The dark bits exist when you want them to and the funny bits do as well. That’s fine.
It’s not fine when you have them all happen at once in a pack of trading cards, for the same reason that it wouldn’t be fine if a film showed you all these things at once. Everything pulls in different directions— without one consistent setting and tone for the set, it all blends into a strange and dissonant mess.
It also… you can’t tell a twist narrative when a person receives all the scenes out of order? This should be obvious. The killer in the set’s mystery is revealed on a common. The suspects in the mystery aren’t indicated to be suspects on the cards where they appear. You can’t actually tell a murder mystery in this given form because you can’t control when information is received! The whole thing is fundamentally misconceived.
For all we’ve been told that we have to already care about the suspects in a mystery… I think it’s fairly clear the opposite is true. Nobody gives a shit about what Reverend Green is doing once your game with him is over. What is important is to have clear archtypes, which is what real murder mysteries and workable settings in murder mystery games tend to do. The cash-strapped young heir, the twitchy ex-military type, and so on.
I think having a set based around those would have worked a lot better than this? Something like Wilds of Eldraine’s goal that the player tells their own fairy tale every game. It would be much better for the player to be in control over their own mystery.
So: I think this is good reasoning, but the reasoning is applied to the wrong product. I think that’s important to stress because I got the impression that internally WotC did the same— they made decisions that would make for an excellent narrative story, but a confusing and ugly setting to be playing a game in. And I think that means they fairly clearly made the wrong decision, here. It doesn’t feel like this set put the game itself first and foremost.
