I mostly agree with you.

But you have stated an absolute. “Science isn’t science without collaboration.”

I don't think that's what I'm saying, at least, that's not my stance. I'm trying to say that how we formally define Science is one thing. But in practice, Science can only be collaborative because of the complexity of topics, the nuance that needs to be captured in experimental design, and the human error that needs to be avoided. There's also the connotation that science is the collective body beyond its works that encompasses a community, a culture, a history, a way of thinking, and so on. If you're "doing science", then we have the mutual understanding that you're participating in all of the above, because otherwise, you're just conducting independent research that could eventually find its way into the whole.

But if it doesn't ever find its way into the greater body of science, how can we label that as doing science if it hasn't made an impact besides personal profits? And even if those findings work as advertised in a product, how do we know that the hand-waiving explanation in this black box isn't true? It does nothing for our understanding. I won't argue that it works as a colloquial term because a theory could mean whatever possibility popped into someone's head even if it's wrong. Strictly speaking, a theory is much more than a plausible thought and I think that analogy carries on.

you are relegating the likes of great scientists like Newton, Cavendish, Mendel, and Killing to the title of mere “researchers.”

That's a relic of what worked back then but their independent research eventually made it into the science, which is consistent with what I'm saying. Labeling them as researchers takes nothing away from their great achievements. I see no issue with calling an apple a fruit when broadly speaking.