This is a 23-year-old game we're talking about here.
The design work was complete long before anyone working on this project was hired by Ubisoft, and proven in the form of a game that shipped several console generations ago. Ubisoft presumably still has all of the original art assets for reference.
All that had to be done was to study the original game code, port it for modern systems, and then polish up the visuals some. Not a trivial amount of work by any means, but much, much easier than starting from scratch and making a game from nothing.
This should've been a layup for any competent studio given SEVEN YEARS(!!!) to work on the project.
That it wasn't, is undeniable evidence of a AAA game development competency crisis.
It depends what you mean by "original".
The very first Prince of Persia game came out in the early 90s. It's at least 35 years old. It was noteworthy as being one of the first games (if not the first) to have ragdoll physics for the movement of the player.
It was a game of playing through 12 levels (IIRC) and if you died, you started over completely. I played it for 20 hours straight at one point and ended up beating it. I think it takes like 30-45 minutes for a full run through normally? I'm a bit fuzzy on this part. It was an amazing game.
What you're talking about is the early 2000s "reboot" that launched a new franchise under the old name and really wasn't that similar to the original other than a setting of being loosely Persian/Arabic. But it wasn't a platform game in the same sense.
The process you describe, of porting the code and polishing the visuals, is for a "remaster". Ubisoft's now-cancelled Sands of Time project was described as a "remake" [1], which generally is a bigger project that keeps the same characters and story beats as the original, but revises the art and gameplay almost as if it were a sequel.
I agree that remakes sound straightforward and it's baffling that Ubisoft couldn't get this one out the door: there are rumors that even before its announcement in 2020, the Sands of Time remake had been started, scrapped, and restarted. But even Nightdive Studios, a perennial remaster maker, struggled for many years with their System Shock remake [2] so it must be harder than it sounds.
I'd love to hear the inside story from folks who've worked on remakes (both released and cancelled) about why they aren't as straightforward as fans expect. Nightdive recently discussed the emotional toll from dealing with angry fans [3] but I haven't seen any interviews discussing the development challenges.
[1] https://en.wikipedia.org/wiki/Video_game_remake#Remaster [2] https://en.wikipedia.org/wiki/System_Shock_(2023_video_game) [3] https://frvr.com/blog/system-shock-remake-lead-couldnt-sleep...