Pedantically speaking, a depressed person can easily have zero drive to do stuff and still be intelligent.
As I said in another comment, "fixed" intelligence implicitly means a fixed ceiling; assuming we all know of intoxication, dementia, etc. is something I think is required by HN standards of being reasonably charitable towards the people you are addressing, also known as the Cooperative Principle.[1]
Implying that I’m being uncharitable is the antithesis of the cooperative principle.
I’m being neither charitable nor uncharitable. I am merely disagreeing with your logic.
As I mentioned elsewhere, I disagree with the idea of a fixed ceiling on intelligence as a general concept.
If you mean performance on narrow tests then I agree there will be ceilings, but that is irrelevant to the general idea.
It makes perfect sense to say that one factor is more important than another if it has more effect on the outcome.
Intelligence is not fixed. It can certainly be decreased by long term stress and environmental toxins etc.
It can also be enabled or inhibited by situational factors such as access to information, available time, etc.
Working ‘harder’ is not well defined. Do you mean going faster at doing the same things, or spending more time working? If not, can you define it?
Working harder or faster on something that is systematically unproductive will only make ones situation worse.
Intelligence is the capacity to select valuable activities in which to invest one’s energy.
Therefore grit doesn’t matter at all in the absence of intelligence, or can even be a negative.