I would say owning your home free and clear is a prerequisite to retire. Rent or payments on debt are often our biggest expenses. Retirement is possible only when passive income is enough to cover expenses.
Switzerland being one of the wealthiest countries in the world with a very good social setup may have something to do with that. In quite a few countries your whole social security payment and then some would be eaten up by rent if you're still renting at that point. Hence the existence of trailer parks and such niceties in other parts of the world.
I would say a prerequisite for safe retirement is to have enough to buy a home outright in cash, otherwise mortgages will weigh you down like a stone:6% interest on a 1 million gbp loan in the UK is unpayable for majority of people even in London and yet you wont find anything worth buying there below that price.
Also we should stop saying a house has equity: it doesn't. You are a paying off a loan for a commodity. A house is like a car or groceries: necessary, yes, but not an investment, unless its luxury. This is how we exploded house prices.
>> huh? why is it impossible for passive income to cover a mortgage?
It's not, but that's a level of passive income that most Americans can not achieve. I suspect it's also structurally impossible for everyone to get there, but yes some individuals can do it.