I don't disagree with you fundamentally. However, needing a visa to come to the UK to study doesn't stop international students coming to the UK and neither does or shoukd it stop UK students from studying in Europe or elsewhere in the world. Lots of the DC's friends have done it post Brexit.
Nothing stops DH and I retiring to France except that we would pay more tax there. Our dc both speak fluent French but it has very little to do with school and formal qualifications.
DD's boyfriend spent school holidays in Germany and speaks fluent German. It is highly likely he will be transferred there in the next year or so.
Freedom of movement around Europe did not commence as soon as we joined the EU or common market, it was introduced in the 80s or early 90s. I am pretty sure I had only 2 European passports between 1975 and 2015. Also, I've endured some horrendous queues coming into the UK from Europe even lre Brexit because we couldn't use the e gates because one of us didn't have the right chip on their passport!
I am old enough to remember the vociferous outcry when we joined the common market about the impact on prices and how terrible a decision joining was. My family were all for it, others were vitriolic about it.
I have no issue with immigration. It is absolutely necessary because due to the structure of our benefit system far too many people in the UK do not have to work. Tell me of another country where someone who has abundant work available can refuse to work more than 16 hours per week because it would impact their universal credit. If issues like that were dealt with, then the desire to come to the land of plenty would diminish.
Brexit has not diminished my dc's opportunities one iota. It didn't stop them going to uni, it didn't stop them doing further post grad quals, it didn't stop them getting good jobs, it doesn't stop them or us hopping on a plane to Europe when we want to. Where I work, all the European people who were employed at Brexit stayed due to the settlement scheme.
I find it really interesting that on the one hand Brits complain about relocating from their home towns to where the work is and moving geographically within the UK, but also complain they no longer have opportunities to work/live in Europe if they wish.