The biggest problem I have with the 401k is that it was very clearly set up as a tax break for the upper class. It was then extended to be the primary retirement for everyone and it has oh so many footguns and ways to bilk retail investors along the way.
1. It's tied to your employer, and not universally available. 2. Even when it's available, it's not mandatory to save anything. It should at the very least have a decent default contribution with a 'I really know what I'm doing' opt out. 3. Investment options are often active funds with subpar performance and high fees 4. It's too easy for retail investors to panic and sell everything during a downturn.
If the government were really intending to set up a defined contribution retirement plan, they should have just made the TSP available 'at cost' to everyone. Autoenroll everyone at 10% in a 'target date' index fund and don't let them touch it until their 60's unless they have a terminal illness or something. It really is that simple.