What makes you think I (or anyone else) wouldn’t know the language? I speak French, Spanish and some Italian. It doesn’t matter whether you speak the language or not, anyway - plenty of English expats don’t! - it’s the principle of freedom of movement.
Britain actually benefitted massively from EU freedom of movement, which filled high-skill labour deficits across our economy for more than a decade — we effectively siphoned off a huge amount of EU talent, from the NHS to universities to finance. Now those people have gone home, we’ve lost the benefit to our economy of excellent Polish plumbers and accountants, Romanian construction workers, Spanish nurses, German scientists and French engineers, etc. etc.
Who have we got instead? Lots of unskilled workers from elsewhere in the world with less good qualifications, many of whom are not remotely as good contributors to our economy as all the EU workers were. And we’ve still got lots of illegal migrants as well. So that was a massive fucking own goal by all the people who didn’t like immigration and were thick enough to think that Brexit would make immigrants go away. (Oh, and no, we don’t train those high skill people ourselves, because as a culture we don’t actually like investing in our own kids or funding education and training. We prefer to load all our young people up with massive debts, ration their access to higher education, and import all our doctors, nurses and lecturers from other counties where they take education more seriously. So those jobs are not suddenly going to British people instead. They’ve just disappeared for the most part.)
We’ve also lost: massive grant incomes for European science projects; the ERASMUS scheme which allowed our students to study in the EU and EU students to come here; we’ve lost all sorts of opportunities for travel and reciprocal exchange amongst cultures, including our own population actually leaving a few more languages and skills from elsewhere in Europe.