BG3 is a success despite its launch was anticipated in August to avoid head-to-head competition Starfield. If we compare the success of BG3 with CyberPunk2077 launch failure, I think we can learn something about software developing PLANNING.
Divinity games are a tactical game with a lot of freedom, you can take things, combine them, and solve quests with different approaches (brute forces, talks with different paths, etc).
For instance you can try to open a door with a key, with a burglar kit, or bashing it until it is destroyed (more long but feasible).
Divinity2 is open world, you can have plenty of quest opened, and it is very loose on character definition. You start with a class, but you can shape all your party, limited to 4 guys, as you want.
The learning curve is steep, because you need to learn a lot of thing, but the tutorial continues to give you hints even after 2 hours of game. The level of details is a lot because you have a crafting, cooking and deal system.
The crafting system is complex, and you can try to eat a lot of different ‘things’ to find out effects: both of these aspects are like the one found on Skyrim.
The merchant system is original: you can make deal with everyone, not just ‘merchants’ and the stuff provided change when your player levels up.
The game was developed on 2017, and optimized in subsequent years. So I think we can easily infer the BG3 engine is derived from that engine, and it is not a full rewrite.
Also Divinity games are medieval RPG like BG3, they lay in the same context (a lot of concepts can be reused) and so the entire software logic can be refactored with ease.
This given Larian Studios the time to refine the game logic, which is very complex. Also it reduced the bugs rate (the software engine was already battle tested).
CDProjectRED, the publisher of Cyberpunk2077, decided instead to try to fill a gap of a game scenario with zero competition (no one had written decent cyberpunk-like games in that time frame); it was a clever market idea, after all.
The project started during end of PS3 realm, aiming at PS4, but they were forced to delay, delay and finally deliver a sub optimal product during PS5 launch windows. The performance on PS4 was so terrible Sony was forced to pull it from the marketplace, increasing the shame and the user base anger. They finally delivered a working version on PC and PS5, but PS4 version was unusable.
Also a lot of weird bugs was reported, with negative advertise and stock market impacts on the Company.
Modern software product are not only software: software is a central piece of the picture, but it it not alone. Cloud providers simplify infrastructure deploy, maintenance and promise linear scalability. But software stabilization must be kept in the loop.
Also, remember software do not rust, so full rewrite are a very risky option.
You can buy Divinity with huge discounts these days: try it on Steam or on your preferred console store (amazon link at right)