Slowing appreciation below inflation is depreciation/losing value. It's a hard tagert to nail, but if we can keep the needle between static price and inflation; we're doing well.
They'd not only lose money on their life savings, they'd be trapped, unable to ever move without paying even more money, or filing bankruptcy if they don't have more money to lose.
This already happens, we just don't hear about it. And we normally blame the homeowner for falling into a preditory trap.
Also the building envelope and internals IS a depreciating asset, always has been. It takes effort to maintain it.
Right now it's just the land values rocketing so high that on many places the crack shacks sitting on top depreciates slower than land value increases. So people's homes are still losing money, it's just the land underneath them goes up faster.