I think as long as they add time to the end or give you a credit back for the time the parks are closed it’s fine. The monthly payments are financing a purchase already made. Otherwise you would need to offer refunds to anyone who already paid upfront.
Luckily my wife and I only hold weekday select passes, so the monthly hit is minimal... but suddenly being in a position myself to have lost a years worth of income to this, I understand the pain. We’re operating under an emergency household budget now, and if I could give Disney back the passes to remove that recurring charge, I would. Every dollar suddenly matters.