As a Brit living in it I would tend to disagree. By the way if you're a leaver I've been looking for someone to cover the additional costs you've voted to put on me, DM if interested.
It isn't a myth, there's a marked difference between having the right to live somewhere and merely the possibility.
Before, it was my right to live in the Netherlands. Now, it is just a possibility.
Thanks to the Withdrawal Agreement, because I already live here, I was given the "right" to apply for a residency, which like 99% of applicants, I received. I can now enjoy that for 5 years, after which I will need sponsorship from a company.
This sponsorship is a key difference, which anyone who has moved to the US can attest to. When your continued existence in a country is contingent on workplace sponsorship the power dynamics between you and your employer are really quite different.
In addition, it's one thing for me in a skilled occupation to be able to leave the country. But I have a friend whose boyfriend may be coming here on an art scholarship. She isn't in a skilled occupation. Before, she would have had the right to come here too. Now, I'm pretty doubtful that she'll be able to join him.
At 24 and probably unlikely to ever leave the UK I wouldn't expect you to understand any of this. But it is the lived reality, previously of every British person leaving the EU and now every British person who leaves the UK.
Edit: But of course, I'm not the first person to explain this to you, and it's not the last time you'll bray to the cheap seats with this mischaracterisation.
Just ignore every other benefit of the EU to make your case.