So much time & effort has been put into the Darkmod branch over literally 2 decades now, not a small part into the rendering and things like soft shadows and ambient occlusion and optimizations, bit by bit by tortured bit. It's not just that they were dozens or 100s of hard won little battles that shouldn't just be tossed out willy nilly, although that too, but the current state of the engine is like a manifestation of the Team's work and devotion built into the engine's DNA. We've really made it our engine for our game. I mean there's always room to consider new optimizations, but this is a pretty fundamental & all encompassing thing.
That's even before you get to the part that as AI-assisted vibe code there are reasons to worry about it being sustainable and well-maintainable. It's also worth noting it's not like one person was just coding stuff in a vacuum for our engine as it is now. Basically every feature got endlessly debated and discussed by the team, especially the rendering side. So there's also respecting the democracy of the team.
I wanted to also say that there's a certain look to our game too we should keep as part of its core character, but I don't know if this would actually change its look, so I'll just throw that idea out as something that might be a consideration.
All that said, it may be worth someone looking into it and seeing if anything valuable could be scooped from it, and then we could have that long discussion about it like any feature proposal. I think it's better to look at pieces on their own merits than just taking the thing wholesale uncritically.