I’m not sure what we are arguing about here. The concept of “science” is fairly new and most people we would think of as “scientists” throughout history, such as Newton, actually considered themselves natural philosophers, hence the P in PhD. The modern concept of science arose as a kind of description of something humans do together. “Science” doesn’t mean figuring out the truth. That wouldn’t make any sense, because philosophy, logic, mathematics, etc, are all concerned with figuring out the truth as well. Science is an institution, a social endeavor (except when it isn’t — need counter examples). The Royal Academy of Sciences was created for that reason, funny enough — because Francis Bacon had pointed out that “science requires an intellectual community” (let’s be honest, humans are fairly dumb on their own — standing on the shoulders of giants and all that).

Anyway, in the mid 1950s there was a now famous work by Thomas Kuhn called The Structure of Scientific Revolutions which added an extra layer to the debate when he pointed out aspects of “science” that seem to be… not about finding the truth at all. But I’m guessing you already know that. Human beings are driven by many motivations, after all, and finding the truth is rarely one of them.

Anyway, the demarcation problem, yes: it’s very difficult to come up with a definition that perfectly picks out legitimate science without also applying to pseudo nonsense (see Pigliucci‘s Nonsense on Stilts). That said, we know what is and isn’t science. We are just having trouble coming up with a perfect definition that works every time.

Incidentally, having trouble defining science is literally my position. Science is something we do that isn’t as tidy and uncomplicated as “figuring out the truth.” It clearly involves some sort of methodology and it clearly involves people checking each other’s work and so on and so forth, and it’s different from math and different from astrology. You tell me how you want to define it, but it sure as shit isn’t “doing stuff in one’s garage alone without writing it down or reproducing the results,“ which is what Elon Musk seems to think.