If you say, “We should have invested more,” I point you to the 40% of current retirees that were not in a position to invest because their jobs didn't pay them enough above the cost of existing. And then there are any number of events, such as age discrimination, common medical issues, divorce, and bankruptcy, that destroy retirement plans.
From what I can tell, it's not possible for the vast majority of the population to be able to save for a 20 plus year retirement.
One of the things that keep people from saving are the activities driven by their investing in the stock market. To increase returns, "Activist investors" and private equity drive companies to shed jobs. You shed a job, you destroy a person's ability to save for retirement, which makes them more dependent on the social contract of Social Security and Medicare.
Cutting benefits will only cause suffering. The cost will fall on society in other ways in terms of elderly homeless people filling the ERs, begging in the streets, or committing suicide. Is it time for a "Modest Proposal II"?