Let's start by using strength as an analogy. A human is strong when they develop their physical body to its potential. That means developing muscles, cardio, lung capacity, flexibility, etc. A human is weak when they fail to develop their physical body to its potential (we don't actually care how strong humans are compared to each other, only to themselves). We can then judge human populations based on, say, the strength of the median person.

Intelligence is the same but for mental faculties. A human is intelligent when they develop their critical thinking, memory, focus, logical reasoning, etc. A human is unintelligent when they fail to develop these things to their personal potential. And when I look around me I see a culture of inustrial-strength distraction that has robbed people of their ability to focus, I see encyclopedias in everyone's pockets that have robbed them of any incentive to remember, I see a society of comfortable complacency that has shielded them from any consequence of poor logical reasoning, and with LLMs I see a mass surrender of the need to exercise critical thinking in exchange for the warm embrace of thoughtlessness.

There's no reason that things need to be this way. The human hardware hasn't fundamentally changed in 100,000 years, and we have so many more resources today that it's easy to imagine that we could all be, collectively, more intelligent than ever if we could somehow inspire people to care. Sadly, we don't seem to be able to.