Every month, your employer transfers Bitcoins into a time-locked address that can't be transferred out before you reach retirement age.  You have the key to the address.  You can verify the transfer on the blockchain.

No middle-men.  No funny business.  No brokers with pyramid/eyeball shaped logos.  No "oops we went bankrupt and lost your retirement."  No bail-ins.  No raising the age of retirement.

Just Bitcoin.