Imagine you have lost keys to the wallet in a boating accident. The contents of your wallet were most likely staked, as 73% of circulating supply is.
As you probably know, the pools collect fees from all transactions present in the blocks it produces, then distributes the reward among stakeholders. All of them, including your wallet where nobody will ever claim the rewards.
The amount of lost ADA rises with each block. As it grows, it attracts more and more rewards. The dead wallet will HODL forever, sucking in everything and spending nothing.
It is like a black hole, which sucks everything in and grows, making their gravitational attraction even stronger as the time passes. It is most likely the terminal state of the matter in the Universe. Eventually, after gazillion of years, there will be nothing left except dark, cold black holes.
Likewise, the dead wallets will bring apocalypse upon the entire ecosystem. Slowly but inevitably they will suck in all ADA in circulation and leave nothing.
Cardano is doomed.