Although, I guess maybe my argument is moot since your average home PC CPU is going to have at least 4, probably more, cores...
For example, Dwarf Fortress is one of the most complicated games of all time, and the creator wrote about how he kept to just running it on 1 core.
On top of that, you need to test it, which means it's much more time consuming.
I'd be surprised if any complex modern game had multithreaded gameplay code, and even if they do, it's usually some common, but CPU intensive problems, like pathing that gets parallelized.
Additionally, I found that most people don't have the skillset to write correct multithreaded code in any capacity, and even those that do frequently introduce hard to detect bugs, in addition to being a huge mental overhead.
It's even harder to make performance gains using multithreading. Let's say I multithread my code, but the additional complexity, and synchronization makes my code run at 60% the original speed. On 2 threads, I'm running at 120% speed. It would've been much easier to keep my code on 1 thread, and invest the mental energy to make the code 20% faster there.
- the behavior of npcs is way more complex here. They’re not just running off scared. The ones at the registers have a way more complex animation than the current gen game.
- the cops seem to have a more refined line of sight and search pattern. They don’t just come at you.
- there is way more use of interiors here, in the current gen there are very few interiors other than instanced garages and stuff.
Nothing else really stood out but it’s clear that even if the graphics are not updated they’ll still have plenty of improvements to gameplay mechanics and world depth.