Your new job usually offers healthcare to replace your old. True, the coverage can be different - sometimes greatly so. It’s one of the factors you take into account when deciding to change jobs.
But you still can't move without having a new job lined up in the new place then. As someone who has recently moved to a new place by getting a remote job offer first, I'll tell you that it's a heck of a lot harder than getting a job in person.
Not saying it's not possible to move somewhere sight unseen and without health insurance (since that's presumably what older generations did) but it's still much higher risk than staying put.
That's true, but isn't COBRA extremely expensive though? Of course there are ways to lower relocation risks, but many involve having a fair amount of money saved up. The people the article is talking about don't have money whatsoever (which is the point of moving to places with higher paying jobs and opportunities).
But if you have a preexisting condition, you could be denied you're new job because of it. This creates an environment where the best worker for the job isn't doing it, leading to market inefficiencies.
