Well that's what a chemistry teacher would say, and a literature teacher would say literature is most important because it lets us understand our place in society etc. etc. The computer science teacher would say every white collar worker now works with computers, it has transformed the world as we know it, that's the most important one.
The English-as-a-foreign-language teacher would say learning English is the most important thing as it opens up the window to all the sciences, all the international news, communication across cultures, just about all employees today in any industry need to know English etc.
But of course history is the most important one because [...].
No, actually sport (PE) is the most important one, because [stats about obesity, heart disease etc.]
Or wait, no actually, scratch all that, the most important thing kids should learn is practical everyday skills, not ivory tower stuff they'll never use. So basic finance, taxes, credits, budgeting, elections, etc. all the way.
It's a trope that teachers always think their subject is the most important and give an amount of homework as if no other subject existed and students could spend all afternoon preparing for just that class.
Although as I read my comment, I think this would be pretty nice: if teachers actually pitched their subjects. But they usually just act as if it's the most important one, without arguing it.
The underlying assumption is reductionism: if we understood atoms best, we can understand and control everything built on them. I am not sure that I can agree with you on that. Complexity makes that a pipe dream.