I feel like people have a tendency to miss the actual meaning of the idea of the IQ in modern psychology. It doesn't help that the name "intelligence quotient" is also super misleading. By current standards, your IQ is -mostly- genetic; this is why they can test someone at about age 7 and determine their overall IQ and it probably won't change more than a few points during their lifetime if they were to be tested again, no matter how much you "train" them. Every psychology professor I've had has labeled IQ not as someone's overall intelligence, but as their POTENTIAL for intelligence. What I mean by that is this:
Imagine that our brains are buckets of all different shapes and sizes; this is a result of mostly genetics and maybe a little bit of our environment during the first few years of life. Some buckets are very large and have a very wide top, so it's very easy to fill them and they can hold a lot of stuff. Some buckets are small and have a weird lid in the way that makes it difficult to fill them and they don't have much room for a lot of stuff. This is basically what the idea of the IQ is intended to represent from a psychological standpoint - the size and shape of our buckets, or our buckets' potentials to obtain and store stuff.
So, with this perspective, think of it like this: Sarah can have a huge and wide-mouthed bucket, while her friend, John, has a smaller, more difficult bucket to use. Sarah learned and retained information really easily, so she realized early on that she didn't have to work quite as hard as John to fill her bucket. Maybe Sarah even went about her life doing nothing but boasting about her bucket rather than actually working to fill it, but John actually worked to fill his, eventually filling his bucket more than Sarah's and learning valuable work ethics and hitting key points of maturity along the way. So, though Sarah started off with the advantage, who is actually better: Sarah, or John?
That being said, the IQ is really hard to record as concrete data because we can't fully agree on what exactly goes into it; this is why there are many different kinds of IQ tests. It's weird for us to put a literal number on something that is so difficult to measure. The major easily tested and recorded trait is someone's ability to think logically because this can be tested with brain teasers and weird math. However, there are many other aspects of one's intelligence that aren't easily tracked. Some examples are creativity, ability to communicate well and actually teach whatever info you retain, and some would even include good work ethics as a trait of intelligence.
So yes, IQ tests help us determine who would be a good engineer because they really only focus on our logical abilities and not much else.