I would argue that the absolute majority of people don't come up with really novel ideas either (and I'm speaking of myself too). Most people just develop existing ideas, and maybe apply them in new contexts.

Now, when you say that do you mean they don't come up with ideas they have never heard of, or that no one has ever heard of? It's not as obvious that most people don't reinvent existing ideas that are new to them.

I would say they rarely come up with ideas no one has ever heard of.

The one they haven't heard of is unlikely to be a truly novel, and more likely just the application of some idea in a new circumstances. (but this starts to be close to a philosophic discussion).

The reason that I thought of this is I was previously discussing about potential for AI in science, and my take was that given how rare are truly novel ideas, I could believe AI in the future can make progress comparable to what many scientists are doing.

The rarity of entirely novel ideas is not the point of contention. What matters is the ability to synthesize fresh concepts from a personal standpoint, akin to how crows and primates can navigate unprecedented situations.

Take book writing as an instance; while it may seem that all conceivable themes have been explored, an individual writer can still originate unique storylines and concepts without prior exposure to similar ideas.

Language models, on the other hand, do not truly invent new ideas; they amalgamate existing ones from their vast repository of training data. What appears to be novel is, upon closer inspection, a recombination of pre-existing information and concepts.