When the premiums go up, people will just drop out of the system.
It’s not foolish to sign up initially, especially if you are getting a whopping subsidy. You can always drop out when the subsidies end and/or the premiums rise.
Meanwhile you may get a couple of free checkups and maybe a free screening or two and you (supposedly) are covered for a catastrophic event should that occur while you are signed up. Pretty good deal for a few people even if it is short lived.
Outrageous cost to everyone else though.