I don't think our problems are as much connected to the age of the candidates the DNC manages to shove on us as it is to the death grip neoliberalism has on both the party and those past their sell-by dates. Obama was a youngster in comparison, but his driving philosophy was centered around the same, proven failed, dedication to free markets to answer all of our society's ills.
We no longer have a strong central government that steps in when private-sector markets fail to provide the security and prosperity guaranteed in our Constitution that posits "government as a service". Instead, we have a money-making machine that serves the elite and their bankers without even suggesting that they use that money for the benefit of the people.
The Democratic Party adopted the Powell Memo with total dedication to free-market capitalism, even to the obvious detriment to its main constituency, the blue-collar working class, They abandoned both the New Deal platform and the unions that represented it in the process and snuggled up to the donor class, much to their own personal enrichment.
Our declining wages and the out-of-control inflation at a time when that donor class is making record profits tells us all we need to know about the priorities of the Democratic Party and its aging leadership. Both are now so close to the Republicans they campaign against that they are now pushing those Republicans to the radical right to give voters some clear motivation for voting Republican.