I agree with guenthert that higher-level intent should theoretically allow for better optimization, but as you said, without the decades of investment that went into the C backends, it's a David vs. Goliath situation.
The 'spiraling complexity' of LLVM you mentioned is exactly why some of us are looking back at leaner designs. For high-density data tasks (like the 5.2M documents in 240MB I'm handling), I'd almost prefer a language that gives me more predictable, transparent control over the machine than one that relies on a million-line optimizer to 'guess' what I'm trying to do. It feels like we are at a crossroads between 'massive compilers' and 'predictable languages' again.