> I find the attitude of people from English-speaking countries that the rest of the world should speak fluent English quite puzzling.
I've noticed the opposite attitude. At least among western countries, the opposition to forcing kids to learn English seems to be far more prevalent among Americans and Brits than among non-anglophones.
In my country, English is mandatory in both primary and secondary education and this is not controversial in any way. It is considered common sense. You mention a lack of significant benefits to people's daily lives - of all the things kids learn in school, what is more useful than learning English? Very basic math certainly as it is necessary to function as an adult, but not much else. I don't remember what the anatomy of an arthropod is like nor do I need this information and I learned a ton of stuff like that in school, while being able to speak (and even more so read) English has opened many doors for me and been useful in so many ways. Academically, professionally and privately.
For anglophones, they and their kids are going to speak English and be fine in the modern world either way. So it is easier for them to virtue signal by dismissing the importance of learning English and supporting some misguided idea of "language equality". A lot of anglophones also don't notice the incredible amount of information in English and the incredible amount of people who speak English to some degree because they take it for granted, causing them to underestimate the usefulness of the language.
Japan may be an exception because it is culturally isolated compared to, for example, the EU. But still, I can't help but think investing more effort in teaching kids English would likely be more useful than at least some things they learn in school, even in Japan.
Also, fluent vs nearly useless is a false dichotomy.