An overreaction and/or exaggeration I think. How hard have you looked at the problem? Without a doubt, there are common aspects of many kinds of intelligence.
Yes. The more I look at it, the more I see the concept of general intelligence as a nonsensical one. What matters is how good you are at solving a given task. I don't think there's any good signal for general ability to solve tasks.
> The more I look at it, the more I see the concept of general intelligence as a nonsensical one.
"nonsensical"? This isn't the right word, is it?
The idea of general intelligence is certainly sensical, in the sense that it is a coherent idea that is not inherently self-contradictory.
The idea of general intelligence is also testable. Run experiments and see how people do across a range of tasks. If you run a set of proper experiments and still cannot find any people that do better across the board, such a result would probably suggest there is no "general" intelligence in humans.
This is not the case however. Such experiments have been run. In humans, there are definitely people who perform better across the board. They almost certainly have better brains (in some sense, though I'm not ruling out more holistic explanations, such as better energy reserves and better microbial health in their guts. (I'm not saying they are "better" people in any moral sense, to be clear).
Now, you might say "ok, but their brains require more energy" or "they have a leg-up somehow". Perhaps, but irrelevant to my core point: there is such a thing as generalizable intelligence. (I didn't say perfectly generalizable, of course.)
I could go along with that, but then I'd want a definition of personhood that excludes chatbots, facial recognition systems, cunning squirrels, and other task-solvers. (Does "solve" even fit with "task"? Well, whatever.)