That is a more reasonable position than trying to imagine or push a single language. And yes, acknowledging it’s not everywhere necessarily, it does seem like multilingualism is fairly automatic out of necessity in much of the world. As an American, I’m sad that the US scores so poorly on multilingualism. I’m very impressed when I travel how many people speak multiple languages. There are so many places where even entry level jobs require 2 or 3 languages.
Yeah, I know people's intuitions are also different there, as almost everyone I've met from Europe speaks 2-4 languages fluently and doesn't consider this exceptional. That makes multilingualism feel very attainable, because it's socially normal. From the U.S. point of view this is amazing, because it's taken for granted there, where it might be a celebrated achievement here.
What I know less about is how much time or effort that multilingualism took, whether peer pressure forced some reluctant kids to stick with languages they were otherwise less interested in, and whether there are any hidden costs.
An example could be replacement of some native vocabulary by English vocabulary (which is happening in many languages). This is a benefit for many people who work internationally, but it probably harms intergenerational understanding on some topics. For example, a Brazilian friend of mine gave a computing history lecture where he noted that Brazilians briefly used Portuguese vocabulary for computer engineering in the 1970s before it was supplanted by English loanwords. That change might mean that older speakers would understand younger speakers less well on some technical topics, or that younger speakers would have a harder time reading older technical documentation. From the point of view of monolingual Portuguese speakers, the internationalization of that vocabulary might not seem like a pure advantage.
I also know that some majority language speakers in Finland (who probably expect to speak English with non-Finnish speakers) greatly resent having to spend a lot of time studying Swedish, the "other national language", if they don't anticipate using it in their day-to-day lives.
In that case, it feels to some of them like the government is requiring them to be multilingual in a specific way that isn't their own preference or that doesn't align with their existing sense of ethnolinguistic identity. It doesn't seem like it's doing any kind of long-term harm, but I guess having any mandatory school subject that you don't enjoy can be pretty unpleasant, and maybe give you a more negative experience of formal education in general.
Some of the Swedish minority there doesn't prefer a future in which Finnish speakers only speak English to them (a phenomenon that already exists and that I think is growing over time). Even though it's officially legally protected, the practical status of their local minority language is being eroded by international culture.
I also have a native Finnish-speaking friend who enjoyed learning Swedish as a foreign language as a child, and ended up moving to Sweden and becoming a university lecturer (who usually teaches in Swedish). Foreign language learning can always be a benefit to anyone of any background.
To again brainstorm trade-offs, it's possible that that outcome is a bit disagreeable to her family back in Finland (who might have preferred her to stay closer to where she grew up, which might have been more likely if she had been more monolingual).
