Not that Unreal Engine 5 can handle a world like CP77 either, despite what people may think with the Matrix demo.
Why can't Unreal handle something like CP2077? Could be an "explain like I'm five" - details would be cool but I'm not sure I would even fully understand them, haha.
Think of it like using the wrong data structure for the problem.
I just assumed in 99% of cases, you could just "tweak" Unreal but if its issues with core components of the engine... I could see why an engine from scratch may work better.
Video games use a trick called Level Of Detail, which means if something is far away, you only render a very low definition version of that object, UE5 has it as well, however we don't know if it's capable enough for something like Night City, obviously the RED engine was built with a very hardcore LOD system that might be a massive pain to do in UE5.
I also have my doubts if they would haven been able to do the same thing better on older consoles with Unreal Engine.
Most of the worst issues with CP2077 have nothing to do with the game engine, things like the NPC AI and broken difficulty curve, the rough melee combat and hiring a shady testing company.
The one thing that could be blamed on the engine is the potentially difficult tooling for the content creators, which can easily be solved, just look at the amount of mods out there.
From the outside, this looks more like a business decision rather than a technical one, that's not to say that it could not work out for CDPR if Epic works with them very closely, however I'm very annoyed when games journalists imply that CP2077 would have been amazing at launch if they would have used Unreal.
Here’s a dumb question: in theory, would Rockstar’s internal engine (RAGE) have worked for CP77, or are the technical challenges simply too different?
Also, I think there are other engines that do as well as RAGE, but none of them are licensed for external use either and are secret sauce to their various developers.
Are there other internal engines that have been used for open-world games with detail and scale at the level of GTA or RDR?
Volition's multiple unnamed/unbranded engines for the Saints Row franchise.
The RenderWare fork used for Crackdown 1. The unknown engine for Crackdown 2 (presumed to be an iteration of the Crackdown 1 engine). (Crackdown 3 used Unreal Engine 4. Useful to mention for those elsewhere in this thread concerned Unreal "can't" do it.)
You can argue that BioWare has tried its raw best to push EA DICE's Frostbite engine as much as possible in that direction. DAI and MEA didn't have truly seamless open-world games, but they tried to get the biggest scale of levels that Frostbite seemed capable of and at their best felt "close". (Obviously at their worst they felt nothing at all like GTA/RDR level of detail/size.)