Some of you guys go out of your way to show how computer illiterate you are. lol
When the tech update was first announced it was clearly laid out that what he was doing is rebuilding the entire game. How are any of you surprised that this is what happened unless you didn't understand a word of the explanation for the tech update?
Yeah, rebuilding the source code from scratch means that every part of the game has to be rebuilt too.
On the coding side, this game is basically a new game now. You can't just copy-paste an old game's code base into a new game's code base and hit a compile button. That's not how software development works. lol
Look, I don't know how exactly the code for STS works, and even less how the team works on it. All I know is the Tech Update was advertised as a "de-spagghettification" of DC's original code from way back when, so yeah, basically re-doing everything from scratch. Everyone (should!) knows that this first slice of the original content being released today isn't 100% of the work they did during these years, and that the "under-the-hood" code is probably mostly done by now (seen as you can explore many different locations and such)
I will give my input when it comes to Ren'Py. This is not an engine exactly built with sandbox open-world roaming in mind at all, but rather, Kinetic Novels powered by Python. In fact, there is a very scarce amount of information on how to even do it in the first place, which means most devs will have to improvise their own systems to bring it to life (I know I did lol)
With that said, I was heavily inspired to make my game open world because of STS as well as many others. I was relatively knowledgeable with programming before starting, but had absolutely no clue about Ren'Py, and winged my way through the early stages of development.
From the ground up, knowing nothing about Ren'Py and alone, it took me about 3 months to get my sandbox environment ready enough to make me feel confident in the project - Daily and Weekly cycles, New locations, Different events at different locations, triggers for unique events and so on.
I do not believe my game is as vast and intricate as STS, particularly when it comes to how things react to your progress with different characters and so on. But I cannot understand how or why did it take so long for a team of developers, with the backing they have, to build STS 100% from scratch.
I could be wrong, but it always seemed that DC was ahead of the schedule with his art, and that most of the progress was being bottlenecked by coding and posing. I have been continuously baffled by this long wait ever since I learned Ren'Py myself, because I simply can't fathom what warrants this much coding effort.
I just genuinely hope that they've at least made the foundations for the game to be easily expandable in the future, so they don't face this bottleneck again. After all, I'm pretty sure this was their main goal from the start, but wow did it take long...