That's a sweet story. My own parents grew up in the Depression, fought in the war, and stayed together until my dad died. (Mom had been married once before, briefly. We were shocked to discover that.)
But this is just 'anecdotal evidence'. There's no real evidence that marriages were any happier in general in the Good Old Days than today. The difference is that there was a huge stigma against divorce and divorced people. If a divorced woman moved into a neighborhood in the 40s or 50s, there was a lot of nasty gossip all around the neighborhood that she was shopping around for other womens' husbands.
Divorce lost its stigma in the 60s and 70s and divorce laws were liberalized across the country to make it easier for people to get out of bad marriages. And for a while the divorce rate rose significantly. But once all the people who'd been trapped in unhappy marriages got their divorce, the rate lowered to less than it had been before! Today the divorce rate is slowly falling year by year.
But fewer people are getting married these days, more are just living together for years and years. More people are deciding not to have children so we've redefined the whole concept of 'family'. This has led to some social upheaval but it's just people getting used to the new setup, the new way things are. Things are different today from your grandparents' time!