If this was true, we'd see landlords with paid-off mortgages waiving the rent. Since we don't see this on any major scale, we can only conclude that mortgages are inconsequential to landlords demanding rent-payments.

A mortgage is not the only cost of owning a property. Taxes are a third of my mortgage payment every month. Other than the IRS delaying tax day by 3 months, I haven't seen any delay or waivers of taxes due.

In addition, there's basic upkeep and maintenance that you're required to perform to keep a building insured, let alone to make it re-openable at some point.

That’s because pensioners and investors expect to be paid their due.

Strikes me the gym and the bank could probably come to some kind of arrangement?

I think the Landlord would feel left out if so.