I don't think the 401k is failing most of these folks because they mis-manage the money(pick the wrong funds, investments, etc...). I think it is failing them because they lack the finanical discipline to actually contribute the proper amount. Some that do initially ruin their plan buy doing hardship withdrawals or constantly doing 401k loans.
Probably, but the reason that the 401k has failed doesn't really matter. What matters is that the 30 year experiment with the 401k failed to provide a generation with an adequate retirement. So, it should be replaced and my choice would be to increase SS since that program has been successful over nearly 80 years.