Perhaps you’re just talking to the wrong older people. Talk to more of them – perhaps in different places and different situations than the ones you’ve been finding.
In any case, it’s not a “genetic” predisposition if it relates to aging, is it?
Most of the starting responses to this question are clearly correct in their ways; I don’t think that I would dispute many of those responses.
In many cases and in many ways things were better “in the olden days”. Kids played outside more, and with less supervision, and it wasn’t necessary for them to have guardians every minute of the day. In fact, here’s something: Things were better in the olden days because I was a kid then.
In your example on crime, for example, it’s very rare for a child to be the victim of a mugging, and very few children in the 1960s-80s were mugged. Mugging victims are more likely to be adults, and these days, more likely to be elderly adults. So despite the validity of statistics showing that muggings and other crimes are declining, the fact is that elderly people today are more likely to be victims of that kind of crime than they were as children. So in their eyes things have gotten objectively worse, despite your statistical evidence to the contrary.
In so many other ways as people age things get objectively worse: their friends die off faster; their own health declines; their eyesight and hearing decline; their memories worsen. You can name all of the other various age-related things that will happen to a person that will degrade the quality of his or her own life. It’s hard for people to control for these things when they compare “now” to “then”.
You must make allowances for where people are in their own lives when you ask such questions, and make allowance for their response, too.