In today's world, it is clear that the old voters are robbing the young of a lifestyle that the young want. The old live with a mental model that is far removed from what the young want.
The young from the UK can still apply for a visa, like the young from many other countries not in the EU. They also have a higher chance of getting one, probably.
Another factor is that the core Brexit (and Conservative) voters are retired home-owners, who are less directly connected to the productive side of the economy. The media they consume keeps them in that fantasy bubble. Take the Daily Express for example, which has reality-defying headlines that would put the North Korean Ministry of Information to shame.
So other than some clues (rising prices that can be blamed on global conditions, longer queues at airports that can be blamed on staff shortages and so on) they probably believe Brexit is going just fine.