Ironically, this is similar to the original logic of the IQ test. If you are able to pick up and figure out the given questions quickly, you should be able to pick up and figure out many other things quickly, which is a pretty normal definition of intelligence.

There is no shortage of people who will do poorly at IQ tests because of cognitive difficulties and (sure) lack of motivation to practice. Does loading on factors like these make IQ tests less predictive of academic or career outcomes? No, both of those things also require a combination of cognitive ability and motivation.