But that's my point - it's hard just getting it to work. Getting it to work fast is next level. Games are notorious for garbage tier SW engineering practices, bugs, ship and forget, and it's all about making something look like you'd expect it vs. making it correct - just completely different goals.
Half-life 2 is possibly one of the most impressive, in terms of combination of complexity, stability, flexibility and extensibility, pieces of software ever created. It spawned dozens of other games that all sold millions of copies and offered completely different but high-quality experiences. Sure, your typical AAA game isn't near this level of perfection, but your typical non-game software is hardly any better.
I like hl2 and all, but I doubt it would be even close in complexity to a web browser/OS kernel/good performing virtual runtime, like the JVM, compilers.
There are insanely complex programs out there.
Hilariously, I wouldn't even say that modern software does that well either.