To unpack the word, IQ approximately means how complex concepts can you "juggle" in your head

I think I agree with this, this is why I don't understand how can intelligence be defined as goal-achieving ability. When I am struggling with the hardest exercises on the Raven test, what I wish I had more is not some goal-achieving power but something far simpler, something akin to short term memory. So when I wish for more intelligene, I just wish for a bit more RAM in short-term memory, so more detailed, more granular ideas can be uploaded into tumble space. No idea why should it mean goal-achieving or optimizing ability. And for AI IQ sounds like entirely hardware...