Just to be clear here, if an architect copies the original building, he's creative, but if he copied it from a video game he's a hack, right?
Yes and no
To be clear, there is no original Anor Londo to copy. A copy is a wholesale reproduction of a thing done in the same or similar medium, not parts taken and rearranged here and there in an entirely different medium. The production design team referenced real life architecture from various sources to create a single structure that doesn't exist in real life, in entirely different medium. Unless somewhere out there are cathedrals with rotating platforms powered by giant levers, with the exact same placement of every spire, walkway, and window, of the same scale, illuminated by a perpetually setting sun, etc.
An artist working in any kind of mimetic visual art is not only supposed to be inspired by real life first and foremost, if his work is to have any chance of originality (not in the sense of being the first of its kind ever, which is nearly impossible) or authenticity, he can hardly do otherwise. There is nothing that he can come up with that his observable universe hasn't provided in some way, even working in fantasy. If there were no reality to observe or we could not observe it, there would be no such art at all. The charge of copying or ripping off cannot be leveled at him. There is no choice in the matter unless mankind's powers of visualization and conception were to change.
To be fair, without having seen to the degree which the environment is the same in Code Vein, I can't damn it as hack work or say they ripped off or copied anyone. But it's suspect considering how influenced they are by Dark Souls. But it would be hacky if they did straight put Anor Londo into their game, and any concept design instructor or high level professional would vomit at the thought, and even referencing other's work as your starting point is generally frowned upon, for various reasons. To me, your comment suggested there is parity between sourcing real life and rubber stamping from another person's work, the former justifying the latter, and I passionately disagree. But if both games did replicate an actual location 1 to 1, then yeah, fair game.