IQ is as proxy for problem solving if the problems look like a standardized test. The problems people face in the real world require more specialization and a more complex combination of skills and traits.
Pattern recognition in obviously helpful when problem solving.
if you think those outcomes are decent proxies for intelligence then IQ is useful
What you're pointing out is that crystalized intelligence is what matters.
Fluid intelligence mediates the ability to gain crystalized intelligence.
Higher IQ in theory means you should get further faster. Though even without if you are dedicated enough to obtain the same level of crystalized intelligence you might be able to do so. I suspect at some point the cognitive ceilings are different, but who knows by how much.
Third, eat right, exercise, live right, etc. Performance is impacted by health and even supposedly high IQ people will perform worse if they are sick, short of sleep, etc.
IQ isn't a useless concept, but I'm somewhat well versed in the history of IQ tests, etc, and it's got a lot of issues with it.
I think a person with a high IQ could be a great poker OR a great negotiator OR a great writer. Perhaps 2-3 total.